Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Bukhari :: Book 5 :: Volume 59 :: Hadith 459
Narrated Ibn Muhairiz:
I entered the Mosque and saw Abu Said Al-Khudri and sat beside him and asked him about Al-Azl (i.e. coitus interruptus). Abu Said said, "We went out with Allah's Apostle for the Ghazwa of Banu Al-Mustaliq and we received captives from among the Arab captives and we desired women and celibacy became hard on us and we loved to do coitus interruptus. So when we intended to do coitus interrupt us, we said, 'How can we do coitus interruptus before asking Allah's Apostle who is present among us?" We asked (him) about it and he said, 'It is better for you not to do so, for if any soul (till the Day of Resurrection) is predestined to exist, it will exist."