I have a slave-girl and I practise 'azl with her, whereupon Allah's Messenger (ﷺ) said: This cannot prevent that which Allah has decreed. The person then came (after some time) and said: Messenger of Allah, the slave-girl about whom I talked to you has conceived, whereupon Allah's Messeuger (ﷺ) said: I am the servant of Allah and His Messenger.
Sahih Muslim Book 16, Hadith 159
← Previous Hadith I have a slave-girl who is our servant and she carries water for us and I have intercourse with her, but I do not want her to conceive. He said: Practise 'azl, if you so like, but what is decreed for her will come to her. The person stayed back (for some time) and then came and said: The girl has become pregnant, whereupon he said: I told you what was decreed for her would come to her.

Sahih Muslim Book 16, Hadith 158 Next Hadith → A person came to Allah's Apostle (the rest of the hadith is the same).

Sahih Muslim Book 16, Hadith 160