"Those who take an oath, not to have sexual relations with their wives, must wait four months." Sahih al-Bukhari 5290
Arabic hadith text
حَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، أَنَّ ابْنَ عُمَرَ، رضى الله عنهما كَانَ يَقُولُ فِي الإِيلاَءِ الَّذِي سَمَّى اللَّهُلاَ يَحِلُّ لأَحَدٍ بَعْدَ الأَجَلِ إِلاَّ أَنْ يُمْسِكَ بِالْمَعْرُوفِ، أَوْ يَعْزِمَ بِالطَّلاَقِ، كَمَا أَمَرَ اللَّهُ عَزَّ وَجَلَّ.
Translation
Narrated Nafi`
Ibn `Umar used to say about the Ila (which Allah defined (in the Holy Book), "If the period of Ila expires, then the husband has either to retain his wife in a handsome manner or to divorce her as Allah has ordered."