Ruling on the follower saying the closing salam before the imam due to forgetfulness

From Ras Tanura, a message sent by our brother Uthman Muhammad Ahmad. Our brother: What is the ruling on saying the salam before the imam in a state of forgetfulness? Is his prayer valid or not?
Answer: If the follower says the salam before the imam due to forgetfulness, he should return to the intention of the prayer, then say the salam after his imam, and he owes nothing; his prayer is valid. If he says the salam before his imam due to forgetfulness and then realizes it, he returns to the intention of the prayer, then says the salam after his imam, and he owes nothing, unless he is one who joins the prayer late. If he is one who joins the prayer late by one unit of prayer or more, he performs the prostration for forgetfulness after making up what is due from him. Once he has made up the units of prayer due from him, he performs the prostration for forgetfulness regarding his saying the salam due to forgetfulness before his imam. Yes.