Sahih Bukhari Volume 7, Book 68, Hadith 5292

حَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، أَنَّ ابْنَ عُمَرَ، رضى الله عنهما كَانَ يَقُولُ فِي الإِيلاَءِ الَّذِي سَمَّى اللَّهُ لاَ يَحِلُّ لأَحَدٍ بَعْدَ الأَجَلِ إِلاَّ أَنْ يُمْسِكَ بِالْمَعْرُوفِ، أَوْ يَعْزِمَ بِالطَّلاَقِ، كَمَا أَمَرَ اللَّهُ عَزَّ وَجَلَّ‏

Narrated By 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."