It is narrated from Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him), he says: On the day of Hunayn, we obtained slave girls, and we desired wealth in exchange for them, so we asked the Noble Prophet (peace and blessings be upon him) about coitus interruptus (azl). He (peace and blessings be upon him) said: Do it as long as you deem appropriate, but what Allah has decreed will surely happen. Not all semen results in offspring, (it happens from a single drop).