وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، أَنَّ سَعِيدَ بْنَ الْمُسَيَّبِ، وَأَبَا، بَكْرِ بْنَ عَبْدِ الرَّحْمَنِ كَانَا يَقُولاَنِ فِي الرَّجُلِ يُولِي مِنِ امْرَأَتِهِ إِنَّهَا إِذَا مَضَتِ الأَرْبَعَةُ الأَشْهُرِ فَهِيَ تَطْلِيقَةٌ وَلِزَوْجِهَا عَلَيْهَا الرَّجْعَةُ مَا كَانَتْ فِي الْعِدَّةِ ‏.‏

Yahyarelated to me from Malik from Ibn Shihab that Said al-Musayyab and AbuBakr ibn Abd ar-Rahman said about a man who made a vow to abstain fromintercourse with his wife, "If four months pass it is a divorce. Thehusband can go back to his wife as long as she is in her idda." Translation Not Available

Book Ref: Muwatta Imam Malik Book 29 Hadith 1172
Web Ref:  Muwatta Imam Malik Book 29 Hadith 18