It is narrated from Sayyiduna Abu Sa'id al-Ansari al-Zuraqi (may Allah be pleased with him) that a man from the tribe of Ashja' asked the Messenger of Allah (peace and blessings be upon him), saying: I have a wife who is nursing, and I do not want her to become pregnant; may I practise withdrawal ('azl)? He (peace and blessings be upon him) said: "Whatever has been decreed for the womb will surely come to be."
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 18995