Narrated Ibn 'Umar (RA):

When a period of four months elapses, the one who swears to stay away from his wife must be made to return to her or divorce her, and the divorce is not valid till the husband himself pronounces it. [al-Bukhari reported it].

وَعَنِ اِبْنِ عُمَرَ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: { إِذَا مَضَتْ أَرْبَعَةُ أَشْهُرٍ وَقَفَ اَلْمُؤْلِ ي [1]‏ حَتَّى يُطَلِّقَ, وَلَا يَقَعُ عَلَيْهِ اَلطَّلَاقُ حَتَّى يُطَلِّقَ } .‏ أَخْرَجَهُ اَلْبُخَارِيّ ُ [2]‏ .‏