Musnad Abu Ya'la al-Mawsili 109:250

Abu Khaythama narrated to us, Rawh narrated to us, Ibn Jurayj narrated to us, he said: Abu al-Zubayr informed me that he heard Jabir saying: The Messenger of Allah (peace and blessings of Allah be upon him) secluded himself from his wives for a month. He came out on the morning of the twenty-ninth. Some of the people said: "O Messenger of Allah, we have reached the morning of the twenty-ninth." The Prophet (peace and blessings of Allah be upon him) said: "Indeed, the month is twenty-nine." Then the Prophet (peace and blessings of Allah be upon him) clapped his hands three times: twice with all the fingers, and the third time with nine of them.