Sahih Muslim
The Book of Marriage (Kitab Al-Nikah)
Book Number: 008 / Hadith Number: 3388
Jabir (Allah be pleased with him) reported: We used to practise 'azl during the lifetime of Allah's Messenger (may peace be upon him). This (the news of this practise) reached Allah's Apostle (may peace be upon him), and he did not forbid us.