Muwatta Malik

Yahya related to me from Malik that he had heard that Umar ibn al-Khattab, Abdullah ibn Umar, Abdullah ibn Masud, Salim ibn Abdullah, al-Qasim ibn Muhammad, Ibn Shihab,and Sulayman ibn Yasar all said, ""If a man has vowed to divorce his wife before marrying her and then he breaks his vow, divorce is obligatory for him when he marries her