وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّهُ كَانَ يَقُولُ أَيُّمَا رَجُلٍ آلَى مِنِ امْرَأَتِهِ فَإِنَّهُ إِذَا مَضَتِ الأَرْبَعَةُ الأَشْهُرِ وُقِفَ حَتَّى يُطَلِّقَ أَوْ يَفِيءَ وَلاَ يَقَعُ عَلَيْهِ طَلاَقٌ إِذَا مَضَتِ الأَرْبَعَةُ الأَشْهُرِ حَتَّى يُوقَفَ ‏.‏

Yahya related to me from Malik from Nafi that Abdullah ibn Umarsaid, "When a man makes a vow to abstain from intercourse with hiswife and four months have passed he must declare his intent and eitherhe is divorced or he revokes his vow. Divorce does not occur untilfour months have passed and he continues to abstain." Translation Not Available

Book Ref: Muwatta Imam Malik Book 29 Hadith 1171
Web Ref:  Muwatta Imam Malik Book 29 Hadith 18