Muwatta Malik, Book 29, Hadith 96 (USC-MSA)

Yahya related to me from Malik from Abu'n-Nadr, the mawla of Umar ibn Ubaydullah from Amir ibn Sad ibn Abi Waqqas from his father that he used to practise coitus interruptus.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي النَّضْرِ، مَوْلَى عُمَرَ بْنِ عُبَيْدِ اللَّهِ عَنْ عَامِرِ بْنِ سَعْدِ بْنِ أَبِي وَقَّاصٍ، عَنْ أَبِيهِ، أَنَّهُ كَانَ يَعْزِلُ ‏.‏

sunnah.com

also referenced under: Book 29, Hadith 1261 (In-Book)