Swearing by the life of Allaah is permissible
Question

                I got a letter from someone who said in it “By the life of the One who sent down the Qur’aan.” Is it permissible to swear using this phrase?.
Praise be to Allah.Swearing by the life of the 
    One Who sent down the Qur’aan is swearing by one of the attributes of 
    Allaah, may He be glorified and exalted, namely the attribute of life. The 
    texts of the Prophet’s Sunnah indicate that it is permissible to swear by 
    the attributes of Allaah. These are saheeh texts which are narrated in the
    Saheehs of al-Bukhaari and Muslim, and the scholars quoted them as 
    evidence concerning that. 
Imam al-Bukhaari (may 
    Allaah have mercy on him) said: 
Chapter on swearing by the 
    glory of Allaah and His attributes and words. 
Ibn ‘Abbaas (may Allaah be 
    pleased with him) said: The Prophet  (peace and blessings of Allaah be 
    upon him) used to say: “I seek refuge in Your glory.” Abu Hurayrah said that 
    the Prophet  (peace and blessings of Allaah be upon him) said: “A man 
    will remain between Paradise and Hell and will say: ‘O Lord, turn my face 
    away from the Fire and by Your glory I will not ask You for anything 
    else.’” 
Abu Sa’eed (may Allaah be 
    pleased with him) said: The Prophet  (peace and blessings of Allaah be 
    upon him) said: “Allaah said: ‘You will have that and ten times as much.” 
And Ayyoob (peace be upon 
    him) said: “By Your glory, I cannot do without Your blessing.” End quote. 
Saheeh al-Bukhaari,
    Kitaab al-Aymaan wa’l-Nudhoor (Book of Oaths and Vows), chapter no. 
    12. Although al-Bukhaari quoted these ahaadeeth as mu’allaq reports here, he 
    recorded their isnaads in full elsewhere. 
Imam al-Bayhaqi also 
    narrated these ahaadeeth in al-Sunan al-Kubra (10/41), and included 
    them in a chapter entitled: 
Chapter on what was 
    narrated about swearing by the attributes of Allaah, such as His glory, 
    majesty, power, greatness, words, hearing and so on. 
Under this title he 
    narrated a report from Ibn ‘Umar (may Allaah be pleased with him), which 
    says that he was asked about alcohol and he said, “No, by the hearing of 
    Allaah, it is not permissible to sell it or to buy it.” 
Al-Haafiz Ibn ‘Abd al-Barr 
    (may Allaah have mercy on him) said: 
Swearing by the attributes 
    of Allaah is permissible and expiation is required [if the oath is broken], 
    because they are part of Him, may He be exalted. End quote. 
Al-Istidhkaar 
    (5/205) 
Ibn Rushd (may Allaah have 
    mercy on him) said: 
As for those who regard it 
    as impermissible to swear by the attributes and actions of Allaah, this is a 
    da’eef (weak) view. End quote. 
Bidaayat al-Mujtahid 
    (1/298). 
Shaykh al-Islam Ibn 
    Taymiyah (may Allaah have mercy on him) said: 
It is well known that 
    swearing by His attributes is like swearing by Him, such as if he says “By 
    the glory of Allaah” or “By the life of Allaah” or “By the Holy Qur’aan”. It 
    is proven from the Prophet  (peace and blessings of Allaah be upon him) 
    and the Sahaabah that it is permissible to swear by the divine attributes 
    and the like. And swearing by His attributes is like seeking refuge in them, 
    and refuge can only be sought with Allaah, as in the words of Allaah, “I 
    seek refuge in Your countenance” and “I seek refuge in the perfect words of 
    Allaah” and “I seek refuge in Your pleasure from Your wrath” and so on. This 
    is something that is affirmed by the scholars. End quote. 
Al-Fataawa al-Kubra 
    (4/130). 
This is what has also been 
    stated by the fuqaha’ of the four madhhabs. 
Al-Kaasaani al-Hanafi (may 
    Allaah have mercy on him) said: 
If a person says, “By the 
    glory of Allaah, by the greatness of Allaah, by His Majesty, by His pride”, 
    then he is swearing an oath, because customarily and usually when these 
    attributes are mentioned, what is meant is Allaah Himself. So what the 
    person who swears such an oath intends is to swear an oath by Allaah. 
    Similarly, people are used to swearing oaths by these attributes, and there 
    is no report to suggest that sharee’ah forbids swearing oaths by them. End 
    quote. 
Badaa’i’ al-Sanaa’i’ 
    (3/6). 
The words of the Prophet 
     (peace and blessings of Allaah be upon him), “Whoever wants to swear an 
    oath, let him swear by Allaah” should not be understood as meaning that 
    permissible oaths are limited to swearing by this name only; rather the 
    ruling on all the names of Allaah is the same as the ruling on this name. So 
    if a person swears by al-‘Azeez (the Almighty) or al-‘Aleem (the 
    All-Knowing) or al-Qaadir (the All-Powerful) or al-Samee’ (the All-Hearing) 
    or al-Baseer (the All-Seeing), then it is a permissible oath. There is 
    scholarly consensus on this point. The same ruling applies to an oath sworn 
    by the attributes of Allaah, such as saying “By the glory of Allaah, by His 
    knowledge, by His power” and so on. This is a case where the focus is on the 
    attributes of Allaah. There should be no dispute, because these are oaths 
    like the first kind. End quote. 
Al-Mufhim lima ashkala 
    min Talkhees Saheeh Muslim (4/623). 
Shaykh al-Islam Zakariya 
    al-Ansaari, the imam of the Shaafa’is of his time (may Allaah have mercy on 
    him) said: 
An oath may be sworn by 
    saying “By the knowledge of Allaah, or by His power, or by His truth, or by 
    His greatness, or by His hearing, or by His sight,” and so on. End quote. 
Asna’l-Mataalib Sharh 
    Rawd al-Taalib (4/244). 
Ibn Qudaamah the imam of 
    the Hanbalis of his time (may Allaah have mercy on him) said: 
Swearing by the attributes 
    of Allaah, may He be exalted, is like swearing by His names. End quote. 
Al-Mughni 
    (9/395). 
Shaykh Ibn ‘Uthaymeen (may 
    Allaah have mercy on him) said: 
There is nothing wrong with 
    swearing an oath by saying “By the life of Allaah”, because oaths may be 
    sworn by Allaah, and by any of His names, or by any of His attributes, such 
    as life, knowledge, glory, power and so on. So it is permissible for one who 
    is swearing an oath to say: “By the life of Allaah, by the knowledge of 
    Allaah, by the glory of Allaah, by the power of Allaah” and other attributes 
    of Allaah, may He be glorified and exalted. End quote. 
Majmoo’ Fataawa wa Rasaa’il Ibn ‘Uthaymeen (2/219-220).