Maliks Muwatta Book 29, Hadith Number 100.

Yahya related to me from Malik from Humayd ibn Qays al-Makki that a man called Dhafif said that Ibn Abbas was asked about coitus interruptus. He called a slave-girl of his and said, “Tell them.” She was embarrassed. He said, “It is alright, and I do it myself.”

Malik said, “A man does not practise coitus interruptus with a free woman unless she gives her permission. There is no harm in practising coitus interruptus with a slave-girl without her permission. Someone who has someone else’s slave-girl as a wife, does not practise coitus interruptus with her unless her people give him permission.”