Maliks Muwatta Book 28, Hadith Number 42.
Section : Temporary Marriage.
Yahya related to me from Malik from Ibn Shihab from Urwa ibn az-Zubayr that Khawla ibn Hakim came to Umar ibn al-Khattab and said, ”Rabia ibn Umayya made a temporary marriage with a woman and she is pregnant by him.” Umar ibn al-Khattab went out in dismay dragging his cloak, saying, “This temporary marriage, had I come across it, I would have ordered stoning and done away with it!”