Musnad Ahmad 33:1023

Hassan narrated to us, Zuhair narrated to us, from Abu al-Zubayr, from Jabir: That a man came to the Prophet, peace and blessings of Allah be upon him, 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* (withdrawal) 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."