Musnad Ahmad 33:231

Hashim narrated to us, Zuhayr narrated to us, Abu al-Zubayr narrated to us, from Jabir, who said: A man came to the Messenger of Allah, may Allah bless him and grant him peace, and said: "I have a slave girl, and she is our servant and the one who draws water for us. I have intercourse with her, and I dislike that she should become pregnant." He said: "Practice *azl* (coitus interruptus) with her if you wish, for what is decreed for her will surely come to her." He said: The man stayed away for a while, then he came to him and said: "The slave girl has become pregnant." He said: "I already told you that what is decreed for her will surely come to her."