Virtues of the Ten Days of Dhul Hijjah
Question

How do the first ten days of the Month of Dhul Hijjah differ from other days of the year?
Praise be to Allah.Benefits of seasons of worship 
Praise be to Allah Who has created time and has made some times better than others, some months and days and nights better than others, when rewards are multiplied many times, as a mercy towards His slaves. This encourages them to do more righteous deeds and makes them more eager to worship Him, so that the Muslim renews his efforts to gain a greater share of reward, prepare himself for death and supply himself in readiness for the Day of Judgement.
This season of worship brings many benefits, such as the opportunity to correct one’s faults and make up for any shortcomings or anything that one might have missed. Every one of these special occasions involves some kind of worship through which the slaves may draw closer to Allah, and some kind of blessing through which Allah bestows His favour and mercy upon whomsoever He will. The happy person is the one who makes the most of these special months, days and hours and draws nearer to his Lord during these times through acts of worship; he will most likely be touched by the blessing of Allah and will feel the joy of knowing that he is safe from the flames of Hell. (Ibn Rajab, al-Lataif, p.8)
The Muslim must understand the value of his life, increase his worship of Allah and persist in doing good deeds until the moment of death. Allah says (interpretation of the meaning):
"And worship your Lord until there comes unto you the certainty." [al-Hijr 15:99] The commentators said: "‘The certainty’ means death."
Virtues of the first ten days of Dhul Hijjah
Among the special seasons of worship are the first ten days of Dhul-Hijjah , which Allah has preferred over all the other days of the year. Ibn 'Abbas (may Allah be pleased with him and his father) reported that the Prophet (peace and blessings of Allah be upon him) said: "There are no days in which righteous deeds are more beloved to Allah than these ten days." The people asked, "Not even jihad for the sake of Allah?" He said, "Not even jihad for the sake of Allah, except in the case of a man who went out to fight giving himself and his wealth up for the cause, and came back with nothing." (Reported by al-Bukhari, 2/457).
Ibn 'Abbas (may Allah be pleased with him and his father) also reported that the Prophet (peace and blessings of Allah be upon him) said: "There is no deed more precious in the sight of Allah, nor greater in reward, than a good deed done during the ten days of Sacrifice ." He was asked, "Not even jihad for the sake of Allah?" He said, "Not even jihad for the sake of Allah, except in the case of a man who went out to fight giving himself and his wealth up for the cause, and came back with nothing." (Reported by al-Darimi, 1/357; its isnad is hasan as stated in al-Irwa, 3/398).
These texts and others indicate that these ten days are better than all the other days of the year, with no exceptions, not even the last ten days of Ramadan. But the last ten nights of Ramadan are better, because they include Laylat al-Qadr ("the Night of Decree"), which is better than a thousand months. Thus the various reports may be reconciled. (See Tafsir Ibn Kathir, 5/412).
Reasons behind the virtues of the first ten days of Dhul Hijjah
You should know, my brother in Islam, that the virtue of these ten days is based on many things:

Allah swears an oath by them, and swearing an oath by something is indicative of its importance and great benefit. Allah says (interpretation of the meaning): "By the dawn; by the ten nights" [al-Fajr 89:1-2]. Ibn 'Abbas, Ibn al-Zubayr, Mujahid and others of the earlier and later generations said that this refers to the first ten days of Dhul-Hijjah. Ibn Kathir said: "This is the correct opinion." (Tafsir Ibn Kathir, 8/413)
The Prophet (peace and blessings of Allah be upon him) testified that these are the best days of this world, as we have already quoted above from sahih ahadith.
The Prophet (peace and blessings of Allah be upon him) encouraged people to do righteous deeds because of the virtue of this season for people throughout the world, and also because of the virtue of the place - for the Hujjaj (pilgrims) to the Sacred House of Allah.
The Prophet (peace and blessings of Allah be upon him) commanded us to recite a lot of Tasbih ("Subhan-Allah"), Tahmid ("Al-hamdu Lillah") and Takbir ("Allahu akbar") during this time. ‘Abdullah ibn ‘Umar (may Allah be pleased with him and his father) reported that the Prophet (peace and blessings of Allah be upon him) said: "There are no days greater in the sight of Allah and in which righteous deeds are more beloved to Him than these ten days, so during this time recite a great deal of Tahlil ("La ilaha ill-Allah"), Takbir and Tahmid." (Reported by Ahmad, 7/224; Ahmad Shakir stated that it is sahih).
These ten days include Yawm ‘Arafah (the Day of ‘Arafah ), on which Allah perfected His Religion. Fasting on this day will expiate for the sins of two years. These days also include Yawm al-Nahar (the Day of Sacrifice ), the greatest day of the entire year and the greatest day of Hajj , which combines acts of worship in a way unlike any other day.
These ten days include the days of sacrifice and of Hajj.

Things to avoid in Dhul Hijjah
Question: What must the Muslim avoid during these ten days if he wants to offer a sacrifice?
The Sunnah indicates that the one who wants to offer a sacrifice must stop cutting his hair and nails and removing anything from his skin, from the beginning of the ten days until after he has offered his sacrifice, because the Prophet (peace and blessings of Allah be upon him) said: "When you see the new moon of Dhul-Hijjah, if any one of you wants to offer a sacrifice, then he should stop cutting his hair and nails until he has offered his sacrifice." According to another report he said: "He should not remove (literally, touch) anything from his hair or skin." (reported by Muslim with four isnads, 13/146)
The Prophet’s instruction here makes one thing obligatory and his prohibition makes another haram, according to the soundest opinion, because these commands and prohibitions are unconditional and unavoidable. However, if a person does any of these things deliberately, he must seek Allah’s forgiveness but is not required to offer (an extra) sacrifice in expiation; his sacrifice will be acceptable. Whoever needs to remove some hair, nails, etc. because it is harming him, such as having a broken nail or a wound in a site where there is hair, should do so, and there is nothing wrong with that. The state of ihram is so important that it is permitted to cut one’s hair if leaving it will cause harm. There is nothing wrong with men or women washing their heads during the first ten days of Dhul-Hijjah, because the Prophet (peace and blessings of Allah be upon him) only forbade cutting the hair, not washing it.
The wisdom behind this prohibition of the one who wants to offer a sacrifice from cutting his hair etc., is so that he may resemble those in ihram in some aspects of the rites performed, and so that he may draw closer to Allah by offering the sacrifice. So he leaves his hair and nails alone until the time when he has offered his sacrifice, in the hope that Allah will save him in his entirety from the Fire. And Allah knows best.
If a person has cut his hair or nails during the first ten days of Dhul-Hijjah because he was not planning to offer a sacrifice, then he decides later, during the ten days, to offer a sacrifice, then he must refrain from cutting his hair and nails from the moment he makes this decision.
Some women may delegate their brothers or sons to make the sacrifice on their behalf, then cut their hair during these ten days. This is not correct, because the ruling applies to the one who is offering the sacrifice, whether or not he (or she) delegates someone else to carry out the actual deed. The prohibition does not apply to the person delegated, only to the person who is making the sacrifice, as is indicated in the hadith. The person who is sacrificing on behalf of someone else, for whatever reason, does not have to adhere to this prohibition.
This prohibition appears to apply only to the one who is offering the sacrifice, not to his wife and children, unless any of them is offering a sacrifice in his or her own right, because the Prophet (peace and blessings of Allah be upon him) used to sacrifice "on behalf of the family of Muhammad," but there are no reports that say he forbade them to cut their hair or nails at that time.
If a person was planning to offer a sacrifice, then he decides to go and perform Hajj, he should not cut his hair or nails if he wants to enter ihram, because the Sunnah is only to cut hair and nails when necessary. But if he is performing Tamattu’ [whereby he performs ‘Umrah, comes out of ihram and enters ihram anew for Hajj], he should trim his hair at the end of his ‘Umrah because this is part of the ritual.
The things that are described above as being prohibited for the person who is planning to offer a sacrifice are reported in the hadith quoted above; the person is not forbidden to wear perfume, have marital relations, wear sewn garments, etc.
What to do in Dhul Hijjah
Concerning the types of worship to be performed during these ten days, one must understand that these days are a great blessing from Allah to His slave, which is appreciated properly by the actively righteous. It is the Muslim’s duty to appreciate this blessing and make the most of the opportunity, by devoting these ten days to paying more attention to striving hard in worship. Among His blessings to His slaves, Allah has given us many ways in which to do good and worship Him, so that the Muslim may be constantly active and consistent in his worship of his Lord.
Among the good deeds which the Muslim should strive to do during the first ten days of Dhul-Hijjah are:
    1.Fasting.
It is Sunnah to fast on the ninth day of Dhul-Hijjah , because the Prophet (peace and blessings of Allah be upon him) urged us to do good deeds during this time, and fasting is one of the best of deeds. Allah has chosen fasting for Himself, as is stated in the hadith qudsi: "Allah says: ‘All the deeds of the son of Adam are for him, except for fasting, which is for Me and I am the One Who will reward him for it.’" (Reported by al-Bukhari, 1805).
The Prophet (peace and blessings of Allah be upon him) used to fast on the first nine days of Dhul-Hijjah. It was narrated from Hunaydah ibn Khalid from his wife, that one of the wives of the Prophet (peace and blessings of Allah be upon him) said: The Prophet (peace and blessings of Allah be upon him) used to fast on the first nine days of Dhul-Hijjah and the day of ‘Ashura, and three days each month, the first Monday of the month and two Thursdays. Narrated by al-Nasai, 4/205 and by Abu Dawud; classed as sahih by al-Albani in Sahih Abi Dawud, 2/462.
      2. Takbir . It is Sunnah to say Takbir ("Allahu akbar"), Tahmid ("Al-hamdu Lillah"), Tahlil ("La ilaha ill-Allah") and Tasbih ("Subhan Allah") during the first ten days of Dhul-Hijjah, and to say it loudly in the mosque, the home, the street and every place where it is permitted to remember Allah and mention His name out loud, as an act of worship and as a proclamation of the greatness of Allah, may He be exalted.
Men should recite these phrases out loud, and women should recite them quietly.
Allah says (interpretation of the meaning):
"That they might witness things that are of benefit to them (i.e., reward of Hajj in the Hereafter, and also some worldly gain from trade, etc.), and mention the name of Allah on appointed days, over the beast of cattle that He has provided for them (for sacrifice)..." [al-Hajj 22:28]
The majority of scholars agree that the "appointed days" are the first ten days of Dhul-Hijjah, because of the words of Ibn 'Abbas (may Allah be pleased with him and his father): "The ‘appointed days’ are the first ten days (of Dhul-Hijjah)."
The Takbir may include the words "Allahu akbar, Allahu akbar, la ilaha ill-Allah; wa Allahu akbar wa Lillaahi’l-hamd (Allah is Most Great, Allah is Most Great, there is no god but Allah; Allah is Most Great and to Allah be praise)," as well as other phrases.
Takbir at this time is an aspect of the Sunnah that has been forgotten, especially during the early part of this period, so much so that one hardly ever hears Takbir, except from a few people. This Takbir should be pronounced loudly, in order to revive the Sunnah and as a reminder to the negligent. There is sound evidence that Ibn ‘Umar and Abu Hurayrah (may Allah be pleased with them) used to go out in the marketplace during the first ten days of Dhul-Hijjah, reciting Takbir, and the people would recite Takbir when they heard them. The idea behind reminding the people to recite Takbir is that each one should recite it individually, not in unison, as there is no basis in Shari’ah for doing this.
Reviving aspects of the Sunnah that have been virtually forgotten is a deed that will bring an immense reward, as is indicated by the words of the Prophet (peace and blessings of Allah be upon him): "Whoever revives an aspect of my Sunnah that is forgotten after my death, he will have a reward equivalent to that of the people who follow him, without it detracting in the least from their reward." (Reported by al-Tirmidhi, 7/443; this is a hasan hadith because of corroborating asanid).
      3.Performing Hajj and ‘Umrah. One of the best deeds that one can do during these ten days is to perform Hajj to the Sacred House of Allah. The one whom Allah helps to go on Hajj to His House and to perform all the rituals properly is included in the words of the Prophet (peace and blessings of Allah be upon him): "An accepted Hajj brings no less a reward than Paradise."
    4.Doing more good deeds in general, because good deeds are beloved by Allah and will bring a great reward from Him. Whoever is not able to go to Hajj should occupy himself at this blessed time by worshipping Allah, praying (salah), reading Quran, remembering Allah, making supplication (du’a), giving charity, honouring his parents, upholding the ties of kinship, enjoining what is good and forbidding what is evil, and other good deeds and acts of worship.
      5.Sacrifice. One of the good deeds that will bring a person closer to Allah during these ten days is offering a sacrifice, by choosing a high-quality animal and fattening it, and spending money for the sake of Allah. (more information to follow, in sha Allah).
     6.Sincere repentance . One of the most important things to do during these ten days is to repent sincerely to Allah and to give up all kinds of disobedience and sin. Repentance means coming back to Allah and foregoing all the deeds, open and secret, that He dislikes, out of regret for what has passed, giving it up immediately and being determined never to return to it, but to adhere firmly to the Truth by doing what Allah loves.
If a Muslim commits a sin, he must hasten to repent at once, without delay, firstly because he does not know when he will die, and secondly because one evil deed leads to another.
Repentance at special times is very important because in most cases people’s thoughts turn towards worship at these times, and they are keen to do good, which leads to them recognizing their sins and feeling regret for the past. Repentance is obligatory at all times, but when the Muslim combines sincere repentance with good deeds during the days of most virtue, this is a sign of success, in sha Allah. Allah says (interpretation of the meaning): "But as for him who repented, believed and did righteous deeds, then he will be among those who are successful." [al-Qasas 28:67]
The Muslim should make sure that he does not miss any of these important occasions, because time is passing quickly. Let him prepare himself by doing good deeds which will bring him reward when he is most in need of it, for no matter how much reward he earns, he will find it is less than he needs; the time of departure is at hand, the journey is frightening, delusions are widespread, and the road is long, but Allah is ever watchful, and to Him will we return and render account. As the Quran says (interpretation of the meaning):
"So whosoever does good equal to the weight of an atom, shall see it,
And whosoever does evil equal to the weight of an atom, shall see it." [al-Zalzalah 99:7-8]
There is much to be gained, so make the most of the opportunity afforded by these invaluable and irreplaceable ten days. Hasten to do good works, before death strikes, before one can regret one’s negligence and failure to act, before one is asked to return to a place where no prayers will be answered, before death intervenes between the hopeful one and the things he hopes for, before you are trapped with your deeds in the grave.
O you whose hard heart is as dark as the night, is it not time that your heart was filled with light and became soft? Expose yourself to the gentle breeze of your Lord’s mercy during these ten days, for Allah will cause this breeze to touch whomever He wills, and whoever is touched by it will be happy on the Day of Judgement. May Allah bless our Prophet Muhammad and all his Family and Companions.
And Allah knows best.