From Sahih Muslim (Hadith 4420):
Abu Huraira reported that a person from amongst the Muslims came to Allah's Messenger (ﷺ) while he was in the mosque. He called him saying:Allah's Messenger. I have committed adultery. He (the Holy Prophet) turned away from him, He (again) came round facing him and said to him: Allah's Messenger, I have committed adultery. He (the Holy Prophet) turned away until he did that four times, and as he testified four times against his own self, Allah's Messenger (ﷺ) called him and said: Are you mad? He said: No. He (again) said: Are you married? He said: Yes. Thereupon Allah's Messenger (ﷺ) said: Take him and stone him
Reference: Muslim 4420