Maliks Muwatta Book 029, Hadith Number 004.

Section : The 'Irrevocable' Divorce.

Yahya related to me from Malik from Ibn Shihab that Marwan ibn al-Hakam decided that if someone made three pronouncements of divorce, he had divorced his wife irrevocably.

Malik said, "That is what I like best of what I have heard on the subject."