Chapter 68: Divorce
Narrated Ibn 'Umar: The Prophet (holding out his ten fingers thrice), said, "The month is thus and thus and thus," namely
thirty days. Then (holding out his ten fingers twice and then nine fingers), he said, "It may be thus and
thus and thus," namely twenty nine days. He meant once thirty days and once twenty nine days.
Sahih al-Bukhari 5302