Conditions of Hajj Being Obligatory
Question

What are the conditions of Hajj being obligatory?
Praise be to Allah.Conditions of Obligation of Hajj
The scholars (may Allah have mercy on them) have stated the conditions of Hajj being obligatory , which, if they are met, make it obligatory for a person to perform Hajj, and without them Hajj is not obligatory. 
There are five such conditions: being Muslim, being of sound mind, being an adult, being free and being able to do it. 
Being Muslim 
This applies to all acts of worship, because worship done by a disbeliever is not valid. Allah says (interpretation of the meaning): 
“And nothing prevents their contributions from being accepted from them except that they disbelieved in Allah and in His Messenger.” [al-Tawbah 9:54]
According to the hadith of Mu’adh, when the Prophet (peace and blessings of Allah be upon him) sent him to Yemen, he said: “You are going to people from among the people of the Book. Call them to bear witness that there is no god but Allah and that I am the Messenger of Allah. If they obey you in that, then tell them that Allah has enjoined on them five prayers each day and night. If they obey you in that, then tell them that Allah has enjoined on them charity (zakah) to be taken from their rich and given to their poor.” (Agreed upon)
So the disbeliever is commanded first of all to enter Islam. If he becomes Muslim, then we tell him to pray, give zakah, fast, perform Hajj and all the other duties of Islam. 
Being of sound mind and being an adult 
The Prophet (peace and blessings of Allah be upon him) said: “The pen is lifted from three [and does not record their deeds]: from one who is sleeping, until he wakes up; from a child until he reaches puberty, and from one who is insane until he comes to his senses.” (Narrated by Abu Dawud, 4403; classed as sahih by al-Albani in Sahih Abi Dawud) 
So a child is not obliged to perform Hajj, but if his parents take him for Hajj, his Hajj is valid; the child will have the reward of Hajj and his parents will also have a reward. When a woman lifted up a child and asked, “Is there Hajj for this one?” the Prophet (peace and blessings of Allah be upon him) said: “Yes, and you will have the reward.” (Narrated by Muslim)
Being free 
Hajj is not obligatory for a slave, because he is distracted by his duties towards his master.
Being able to do it 
Allah says (interpretation of the meaning): 
“And Hajj (pilgrimage to Makkah) to the House (Ka‘bah) is a duty that mankind owes to Allah, those who can afford the expenses (for one’s conveyance, provision and residence).” [Aal 'Imran 3:97]
This includes being able both physically and financially. 
What is meant by being physically able is that one is sound in body and can bear the hardship of travelling to the sacred House of Allah. 
Meaning of financial ability in Hajj
Being financially able means that one has enough funds to get to the sacred House of Allah and back again. 
The Standing Committee said (11/30): 
“Being able to do Hajj means that one is sound in body and has means of transportation to reach the sacred House of Allah whether by plane, car or riding animal, or by renting such means, according to his situation, and that he has sufficient provisions to get there and back. That should be surplus to what he needs to spend on those on whom he is obliged to spend, until he returns from Hajj. A woman should also have a husband or mahram with whom to travel to Hajj or ‘Umrah.”
The money that he uses to reach the sacred House should be surplus to his basic needs, the spending enjoined on him by Shari’ah, and what he needs to pay off his debts. 
What is meant by debts here is things that he owes to Allah, such as expiations, and what he owes to other people.
Hajj of one who is in debt
If a person has a debt , and he does not have enough money to both do Hajj and pay off the debt, then he should pay off the debt first and he does not have to go for Hajj. 
Some people think that the reason is that he did not ask permission from the one to whom he owes the money, and that if he gives him permission, then there is nothing wrong with it.  
There is no basis for this thinking, rather the reason is being in debt. It is known that if the lender gives the debtor permission to go for Hajj, that does not mean the debt is waived, and he will not have discharged his duty because of this permission. Hence it should be said to the debtor: Pay off your debt first, then if you have enough left, go for Hajj; otherwise Hajj is not obligatory in your case. 
If the debtor who did not go for Hajj because of his debt dies, then he will meet Allah with his Islam complete and not lacking, because Hajj was not obligatory for him, just as zakah and also Hajj are not obligatory for one who is poor. 
But if he does Hajj before paying off his debt and then dies before paying it off, then he is in danger, because even the martyr is forgiven for everything except debt, so what about anyone else? 
Meaning of spending enjoined by Shari’ah
What is meant by the spending enjoined on him by Shari’ah is what he is obliged by shari’ah to spend on himself and his family, without being either extravagant or stingy. If he is of average means and wants to show signs of richness such as buying an expensive car so that he will look rich, and he does not have enough money to perform Hajj, then he has to sell the car and use that money to perform Hajj, and he should buy a car that suits his situation. His spending on this car is not a kind of spending that is approved of in shari’ah, rather it is extravagance, which is forbidden in Islam. 
What is meant by financially able is that he should have enough for his family until he returns, and he should have an income after he returns to take care of himself and those on whom he spends, such as rent from property, a salary and business earnings, etc.  
Hence he does not have to use the capital of his business, the profit of which he spends on himself and his family, to do Hajj, if that loss of capital will result in a loss of profits which in turn will mean that his family does not have enough. 
The Standing Committee (11/36) was asked about a man who has a sum of money in an Islamic bank and his income came from the profits on that money which gave him enough to live a moderate lifestyle. Is he obliged to do Hajj using that capital, knowing that this would affect his monthly income and stretch his finances unbearably? 
They replied: 
“If your situation is as you describe, you are not obliged to perform Hajj because you are not able to in the manner required by shari’ah. Allah says (interpretation of the meaning): 
“And Hajj (pilgrimage to Makkah) to the House (Ka‘bah) is a duty that mankind owes to Allah, those who can afford the expenses (for one’s conveyance, provision and residence).” [Al 'Imran 3:97]
And He says (interpretation of the meaning): 
“and [Allah] has not laid upon you in religion any hardship.” [al-Hajj 22:78]”  
Meaning of basic needs
What is meant by basic needs is what a person needs a great deal of in his life, and which it is too hard for him to do without, such as books for the seeker of knowledge. So we do not tell him: Sell your books and use the money to go for Hajj, because these are basic needs for him. Similarly if a person needs his car, we do not tell him, Sell it and use the money to go to Hajj. But if he has two cars and he does not need one of them, then he has to sell one of them and use the money to go to Hajj. 
Similarly, a craftsman does not need to sell his tools, because he needs them. And if a man has a car which he uses for work and spends on himself and his family from the money he earns for hiring it out, he does not have to sell it in order to go for Hajj. 
Another basic need is the need to get married. 
If a person needs to get married, that takes precedence over Hajj , otherwise Hajj takes precedence. 
What is meant by being financially able is that a person should have surplus funds that are sufficient for doing Hajj after paying off debts and taking care of shar’i obligations and basic needs. 
If a person is physically and financially able to do Hajj, then he is obliged to hasten to do Hajj. 
If he is not physically and financially able, or if he is physically able but he is poor and has no wealth, then he is not obliged to do Hajj. 
If a person is financially able but he is not physically able, then we look at the matter further. 
If his problem is something that he hopes will disappear, such as a sickness from which he hopes to recover, then he should wait until Allah heals him, then do Hajj.   
If his problem is one for which there is no hope that it will disappear, such as a person with cancer or an old person who cannot do Hajj, then he has to appoint someone to do Hajj on his behalf, and the duty to perform Hajj is not waived because of his physical inability if he is financially able.  
The evidence for that is the report narrated by al-Bukhari (1513) according to which a woman said: “O Messenger of Allah, Allah’s command to the people to perform Hajj has come when my father is an old man and cannot sit firmly in the saddle. Can I perform Hajj on his behalf?” He said: “Yes.” 
The Prophet (peace and blessings of Allah be upon him) agreed with her comment that Hajj was obligatory for her father even though he was physically unable to perform Hajj. 
Can women go to Hajj without a mahram?
In order for Hajj to be obligatory for a woman, it is essential for her to have a mahram with her , and it is not permissible for her to travel for Hajj, whether that is an obligatory or nafl Hajj, without a mahram. The Prophet (peace and blessings of Allah be upon him) said: “No woman should travel except with a mahram.” (Narrated by al-Bukhari, 1862; Muslim 1341) 
The mahram is her husband or one whom it is permanently forbidden for her to marry because of blood ties, breastfeeding or ties through marriage. The husband of a sister, maternal aunt or paternal aunt is not a mahram. 
Some women take this matter lightly and travel with their sister and sister’s husband, or with a maternal aunt and the aunt’s husband, but this is haram, because the sister’s husband or the maternal aunt’s husband is not a mahram, so it is not permissible for her to travel with him. So there is the fear that her Hajj is not proper, for the proper Hajj (Hajj mabrur) is that which is not mixed with any sin, but this woman is sinning throughout her journey until she returns home. 
It is also essential that the mahram be an adult of sound mind, because the aim of the mahram is to protect the woman, and a child or one who is insane cannot do that. 
If a woman does not have a mahram, or she has one but he is unable to travel with her, then she is not obliged to do Hajj. 
Should the wife ask for her husband’s permission to go to Hajj? 
The husband’s permission is not an essential condition of it being obligatory for a woman to do Hajj, rather she is obliged to do Hajj when the conditions of it being obligatory are met, even if her husband does not give permission. 
The Standing Committee said (11/20): 
“The obligatory Hajj is obligatory when the conditions of being able to do it are met, and the husband’s permission is not one of them. It is not permissible for him to forbid her, rather it is prescribed for him to cooperate with her in fulfilling this duty. End quote. 
This has to do with the obligatory Hajj. As for nafl Hajj, Ibn al-Mundhir narrated that the scholars were unanimously agreed that a husband has the right to forbid his wife from doing a nafl Hajj, because the husband’s rights are binding upon her and are not superseded by something that is not obligatory for her. (Al-Mughni, 5/35) 
Reference:
Al-Sharh al-Mumti’ by Sh. Ibn Uthaymin, 7/5-27.