Abu Dawood: Hadith 2200

Tawus said A man called Abu Al Sahba used to ask Ibn "Abbas questions frequently. He asked "Do you know that when a man divorced his wife by three pronouncement before sexual intercourse with her, they (the people) made it a single divorce during the time of the Apostle of Allaah (ﷺ), of Abu Bakr and in the early phase of the caliphate of "Umar?" Ibn "Abbas said "Yes, when a man divorced his wife by three pronouncement before sexual intercourse they made it a single divorce during the time of the Apostle of Allaah (ﷺ), of Abu Bakr and in the early phase of the caliphate of "Umar. When he saw that the people frequently divorced (by three pronouncements) he said "Make them operative on them (i.e., on women)" .