Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: The Prophet Muhammad (peace and blessings be upon him) said: "A month is like this and a month is like this." On one occasion, the Prophet (peace and blessings be upon him) spread out all his fingers three times, and on another occasion, the Prophet (peace and blessings be upon him) spread out all the fingers of both hands, but the third time I folded one finger (meaning that sometimes the month is of twenty-nine days as well).