Should a person who cannot prostrate perform prayers by sitting on the floor or on a chair?

- How should an ill person who can stand and bow down but who cannot prostrate because of a disorder in his knees perform prayers? How does his prayer become valid? 
- He cannot bend his knees due to a disorder in his knees; therefore, he cannot prostrate but he can stand and bow down.

Dear Brother / Sister,

In our religion, responsibilities are determined based on the strength of the slave (al-Baqara, 2/286); the principle of ease exists for the states that are beyond one’s power. (al-Baqara, 2/185) The disorders that prevent fulfilling any of the parts of the prayer are regarded among the reasons for easing. (Abu Dawud, Salah, 181)

Accordingly, what is essential for a person who cannot perform the prayer properly by standing is to perform it by sitting. Such a person can perform the prayer by kneeling down, sitting cross-legged or stretching his legs toward the qiblah based on his state.

As a matter of fact, when a Companion who was ill asked the Prophet (pbuh) how to perform the prayer, he said, "Perform the prayer by standing. If you cannot perform by standing, sit or lie down on your side." (Bukhari, Taqsirus-Salat, 19)

Accordingly;

A person who can stand and can sit but who cannot prostrate needs to start the prayer standing, sit after ruku’ and prostrate by gestures.

A person who can stand but cannot stand up after sitting starts the prayer standing and completes his prayer sitting after prostrating. (Marghinani, al-Hidaya, II, 83-85; Mawsili, al-Ikhtiyar, I, 260)

A person who can stand and can perform ruku’ but cannot sit starts the prayer standing; after ruku’, he performs prostration by gestures by sitting on a stool or something like that.

A person who cannot stand and cannot sit on the ground/floor even by stretching his legs to one side or toward the qiblah sits on a stool, chair, etc. and performs ruku’ and prostration by gestures.

It should not be forgotten that when a person worships his Lord, he should be sincere and try to fulfill the formal conditions determined by the religion.

Therefore, the excuses a believer makes in order to perform prayers on a chair, stool, etc. should persuade his conscience. Slight bodily disorders that will not prevent performing prayers properly should not be put forward as acceptable excuses.

On the other hand, it should be known that placing fixed benches and chairs in mosques with the purpose of performing prayers does not comply with the ambiance and culture of mosques.

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