Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: During the time of the Messenger of Allah (peace and blessings be upon him), of Abu Bakr (may Allah be pleased with him), and for two years of the caliphate of Umar (may Allah be pleased with him), three pronouncements of divorce were counted as one. Then Umar (may Allah be pleased with him) said: "People have begun to hasten in a matter in which they had been given respite; so why should we not enforce it strictly upon them?" So he enforced it upon them.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10870