Firstly: The Definition of Ability
Linguistically, ‘ability’ means the power and capacity to do something.
Technically, one able to do something is someone who has physical and financial capacity. This differs based on people’s situations and practices. It comes down to: being able to ride (for travel) and the availability of provisions and a means of transportation that befit someone like him. The preceding is above and beyond the fulfillment of all duties, financial support, and essential needs.
Secondly: The Ruling of being Able
1. Ability as a condition for Hajj being wajib
Ability is a condition for Hajj being wajib. Ibn Hazm, Ibn Qudamah, al-Qurtubi, and al-Nawawi related consensus on this.
2. Is ability a condition for Hajj being sufficient?
Ability is not a condition for the sufficiency of Hajj. If one lacking ability undergoes hardship by performing Hajj without provisions or transportation, their Hajj is valid and fulfils the fard performance required. This is by agreement of the four schools of jurisprudence.
3. Permission of parents for the fard Hajj
Parents may not prevent their legally accountable child from offering an obligatory Hajj, nor may they require he terminate his state of ihram. He may not obey them in doing so even though it is mustahabb for him to get their permission. This is explicitly mentioned by Hanafi, Shafi`i, and Hanbali jurists, and it is one of two positions of the Maliki  Malikis explicitly mention that parents may prohibit their child from performing a fard act earlier than is required. school.
4. Permission of parents of an optional Hajj
Parents may prevent their child from an optional Hajj performance. This is by agreement of the four schools of jurisprudence.
5. Permission of one’s employer
Whoever wishes to offer the fard Hajj and has a contract which requires him to work during some or all of the days of Hajj should ask their employer’s permission. If they approve one may perform Hajj. Otherwise, one is obliged to fulfil their contractual obligations. This is the fatwa of Ibn Baz, Ibn `Uthaymin, and the Permanent Council.
Thirdly: Categories of Ability
There are four categories of ability with respect to Hajj and `umrah:
1. The able, both physically and financially. Such a person must perform Hajj and `umrah on their own behalf. Consensus on this was related by Ibn Hazm, Ibn Qudamah, and al-Nawawi.
2. The unable, both physically and financially. Hajj and `umrah are not required of such a person. Ibn Hazm, Ibn Qudamah, and al-Nawawi related consensus on this.
3. The physically able but not financially. There is no disagreement that Hajj and `umrah are not required of such a person except if money is not required for their performance.  Ibn Qudamah negated the existence of any disagreement in this matter. This is like a resident of Mecca for whom going to sacred sites poses no difficulty.
4. The financially able but with physical inability that is unlikely to go away. It is wajib for such a person to perform Hajj and `umrah by appointing someone on their behalf.  This is the position of the Shafi`i and Hanbali schools, as will be demonstrated.
Fourthly: General Conditions of Ability for Men and Women
1. Physical ability
Inability to sit stably on a vehicle or a mount
Whoever is unable to sit stably on a vehicle or lacks the strength to hold onto a mount is not required to perform the fard Hajj on their own behalf. This is by agreement of the four schools of jurisprudence. Al-Qurtubi related consensus on the issue that one unable to sit stably on a mount is not required to travel for Hajj.
Is one who is physically unable required to assign a proxy?
It is wajib for one who is physically unable but financially able to perform Hajj by sending a representative on their behalf. This is the position of the Shafi`i and Hanbali schools and one position amongst Hanafis. It is the position of choice of Ibn Hazm and Ibn `Uthaymin.
2. Financial ability
The condition of provisions and transportation
A condition for Hajj being wajib is the ability to afford provisions and transportation above and beyond one’s debts, required financial support, and essential needs. This is the position of the majority: the Hanafis, Shafi`is, and Hanbalis. It is the position of Sahnun and Ibn Habib from amongst the Malikis. It is also the position of the majority of jurists.
Who is required to have transportation
Transportation is a requirement specific to those who are far from Mecca such that the distance between them and it is a distance that permits shortening prayers. As for someone living close by who can walk, transportation is not a consideration for them unless they are unable to walk, such as an old man who cannot walk. This is the position of the majority: the Hanafis, Shafi`is, and Hanbalis.
Basic necessities that must exist above and beyond provisions and transportation
· Financial support for one’s dependents and those one for which one is required to provide for the duration of the travel there and back.
· Whatever one and one’s family need in terms of housing and necessities, such as servants, furniture, and one’s clothing – inasmuch as is moderately acceptable for one in such matters.
· Paying off debts due by him, as they are rights of other people. This is a basic necessity and worthier of being fulfilled. This is true whether the debt is to a human or for the right of Allah the Exalted, such as zakat that is due, expiations, and the like.
Is Hajj or marriage given precedence?
Whoever is obliged to perform Hajj and wishes to get married but only has enough money for one of them should get married if he feels the need for marriage and fears falling into illicit sexual intercourse. This is the position of the majority: the Hanafis, Malikis, and Hanbalis.
3. Safety of the route as a condition of ability
What is meant by safety of the route
What is meant by safety of the route is that the route be generally free of harm such that one’s life and property are safe. This is from the time that people leave for Hajj to the time one returns to their homeland. Ability does not exist without such a condition.
Is safety of the route a condition for Hajj being wajib?
It is not wajib for one who fulfills the conditions of Hajj but does not find a safe route to perform Hajj. This is by agreement of the four schools of jurisprudence.
Fifthly: Conditions of Ability Specific to Women
1. The condition of a mahram
What is meant by a mahram
A woman’s mahram is her husband or one who may never marry her due to being related through blood, nursing, or marriage. He must be a Muslim, have passed puberty, be of sound mind, and is trustworthy. This is because the point behind a mahram is to protect the woman, guard her, and take care of her affairs.
The condition of a mahram for the fard Hajj
The companionship of a mahram is a condition for the fard performance being wajib for a woman. This is the position of the Hanafis and Hanbalis. It is the position of choice of Ibn Baz and Ibn `Uthaymin and the fatwa of the Permanent Council.
The condition of seeking a husband’s permission for an additional performance of Hajj
A woman may not enter into a state of ihram that is beyond what is obligatory without her husband’s permission.  Ibn al-Mundhir and Ibn Qudamah related consensus that it is permissible for a man to prevent his wife from performing an additional Hajj. This is by agreement of the four schools of jurisprudence.
The ruling of a man prohibiting his wife from a fard Hajj performance if a mahram exists
A man may not prohibit his wife from the fard Hajj performance if she fulfills all the conditions of Hajj and finds a mahram. This is the position of the majority: the Hanafis, Malikis, Hanbalis, and one position amongst Shafi`is. It is the position of the majority of scholars.
2. Not being in her `iddah
A condition for Hajj being wajib is that the woman not be in her `iddah during the time in which she will travel for Hajj. This is by agreement of the four schools of jurisprudence.  Hanafis generalized this as holding for every woman in her `iddah whether due to divorce that is irrevocable or revocable, death, or annulment. According to Malikis and Shafi`is, there is no difference between the `iddah of death and divorce. Hanbalis hold that the `iddah that deems Hajj not wajib is that of death to the exclusion of divorce. It is also the position of a group of the Salaf.