Maliks Muwatta Book 29, Hadith Number 7.
Yahya related to me from Malik from Nafi that Abdullah ibn Umar said that statements like “I cut myself off from you”, or “You are abandoned”, were considered as three pronouncements of divorce.
Malik said that any strong statements such as these or others were considered as three pronouncements of divorce for a woman whose marriage had been consummated. In the case of a woman whose marriage had not been consummated, the man was asked to make an oath on his deen, as to whether he had intended one or three pronouncements of divorce. If he had intended one pronouncement, he was asked to make an oath by Allah to confirm it, and he became a suitor among other suitors, because a woman whose marriage had been consummated, required three pronouncements of divorce to make her inaccessible for the husband, whilst only one pronouncement was needed to make a woman whose marriage had not been consummated inaccessible.
Malik added, “That is the best of what I have heard about the matter.”