Habib bin Salah حبيب بن صالح · The Book on Salat (Prayer)

the Prophet said: "It is not allowed for a man to look into the interior of a man's house until he has been given permission, for if he looks, then he has entered. And one who leads people (in Salat) should not supplicate for himself alone with the exclusion of his congregation. If he does, then he has betrayed them. And one is not to stand for Salat while he has to urinate."