Sahih Muslim Book 009, Hadith Number 3491.
Chapter: Pronouncement of three divorces.
Ibn 'Abbas (Allah be pleased with them) reported that the (pronouncement) of three divorces during the lifetime of Allah's Messenger (may peace be upon him) and that of Abu Bakr and two years of the caliphate of Umar (Allah be pleased with him) (was treated) as one. But Umar b. Khattab (Allah be pleased with him) said: Verily the people have begun to hasten in the matter in which they are required to observe respite. So if we had imposed this upon them, and he imposed it upon them.