It is narrated from Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) that some people of Banu Sulaym came to the Prophet (peace and blessings be upon him) and said: "O Messenger of Allah, we get captive women in war, and we practise coitus interruptus ('azl) with them." He (peace and blessings be upon him) said: "Do you really do that?" They said: "Yes." He (peace and blessings be upon him) said: "Any soul that Allah wills to bring forth from a man's loins will surely come forth, whether he (the man) wills it or refuses; so there is no harm upon you if you do not do it."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18443