Sayyidah Judamah bint Wahb (may Allah be pleased with her), the sister of Sayyiduna Ukkashah bin Wahb (may Allah be pleased with him), said: I came to the Messenger of Allah (peace and blessings be upon him) while he (peace and blessings be upon him) was sitting among people, and he was saying: "I intended to forbid ghilah (intercourse with a nursing wife), but then I looked at Persia and Rome and saw that they practise ghilah with their children, and it does not harm their children in any way." And they asked him about 'azl, and he (peace and blessings be upon him) said: "It is al-wa'd al-khafi (a hidden form of burying alive). And when the girl buried alive is asked [Surah al-Takwir: 8]."
Note: The narrations from the Prophet (peace and blessings be upon him) about 'azl are more numerous and are in favour of its permissibility; and whoever regarded it as disliked, that is a mild dislike (tanzihi), not that it is forbidden.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14330