It is narrated from Umm al-Mu'mineen Hazrat Aisha (may Allah be pleased with her) that once the Prophet (peace and blessings be upon him) took an oath that he would not go to his pure wives for a month. After 29 days had passed, the Prophet (peace and blessings be upon him) came to me first. I said, "According to my count, today is the 29th day." The Prophet (peace and blessings be upon him) said, "Sometimes a month is of 29 days."