Muwatta Malik, Book 29, Hadith 1172 (In-Book) ⓘ

Yahya related to me from Malik from Ibn Shihab that Said al-Musayyab and Abu Bakr ibn Abd ar-Rahman said about a man who made a vow to abstain from intercourse with his wife, "If four months pass it is a divorce. The husband can go back to his wife as long as she is in her idda."

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 ‏.‏