Maliks Muwatta Book 36, Hadith Number 17.
Section : Judgement on Men Finding Other Men with Their Wives.
Yahya related to me from Malik from Suhayl ibn Abi Salih as-Samman from his father from Abu Hurayra that Sad ibn Ubada said to the Messenger of Allah, may Allah bless him and grant him peace, “What do you think if I find a man with my wife? Shall I grant him a respite until I bring four witnesses?” The Messenger of Allah, may Allah bless him and grant him peace, replied, “Yes.”