For a Sick Person to Sit and Perform salaah

Q: Salaah-106: What is the ruling about a sick person coming to perform salaah in Jamaa'ah in the Masjid when he performs it sitting down? Is it permissible or not?

Answer: It will be permissible for a sick person to sit rather than stand in salaah when he will fall if he stands, when his illness will worsen by standing or if he experiences unbearable pain when standing. It will however not be permissible to sit and perform salaah when one is able to stand. In fact, the person should stand for as long as he can before sitting own, even if he is able to stand only for the duration of the Takbeer Tahreema. There are people who have the ability to stand for the duration of the Takbeer Tahreema, but still sit when doing so, This is not permissible.: And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2