The ruling on one who prayed while there was impurity on his garment, and he knew of it but did not remember it until after finishing

Question : Shaykh, a man had impurity on his garment, and he knew of it and was aware of it, then he forgot and prayed, and then he remembered it after the prayer was finished. What is required of him?

Answer : I will give you a rule, which is that every prohibited act that a person does while forgetting or being ignorant has no effect, do you understand? So if a person has impurity on him and forgets to wash it and prays while forgetting, his prayer is valid. Likewise, if he did not know about it, and when the prayer ended he found it on his garment or on his body, and it does not prevent water from reaching it, then his prayer is valid. And what indicates this is that the Prophet (peace and blessings be upon him) was informed by Jibril during the prayer that there was filth on his sandals, so the Prophet (peace and blessings be upon him) took them off and did not restart the prayer.