حَدَّثَنَا أَحْمَدُ بْنُ صَالِحٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا ابْنُ جُرَيْجٍ، أَخْبَرَنِي ابْنُ طَاوُسٍ، عَنْ أَبِيهِ، أَنَّ أَبَا الصَّهْبَاءِ، قَالَ لاِبْنِ عَبَّاسٍ أَتَعْلَمُ إِنَّمَا كَانَتِ الثَّلاَثُ تُجْعَلُ وَاحِدَةً عَلَى عَهْدِ النَّبِيِّ صلى الله عليه وسلم وَأَبِي بَكْرٍ وَثَلاَثًا مِنْ إِمَارَةِ عُمَرَ قَالَ ابْنُ عَبَّاسٍ نَعَمْ ‏.‏

Tawus said: Abu al-Sahba' said to Ibn Abbas: Do you know that a divorce by three pronouncements was made a single one during the time of the Prophet (PBUH), and of AbuBakr and in the early days of the caliphate of Umar? He replied: Yes. Translation Not Available

Book Ref: Sunan Abi Dawud Book 13 Hadith 2200
Web Ref:  Sunan Abi Dawud Book 12 Hadith 2194