A Muslim is to pray to the best of his ability, the best he can, due to the statement of the Prophet, may Allaah raise his rank and grant him peace, “A sick person prays standing. If he is unable, then he may pray sitting. If he is unable, then he may pray [laying] on his side.”
Text taken from brother Moosaa Richardson’s website.
How to Pray in a Chair When Needed (Shaykh Saalih Al-Fowzaan)
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How To Pray Salat In A Chair | Shamsi