Musnad Ahmad 1153:2048

Rawh narrated to us, he said: Abu ‘Amir al-Khazzaz narrated to us, from ‘Abdullah ibn Abi Mulaykah, from ‘Aishah, she said: He entered upon me on the twenty-ninth, and I said: "It is not hidden from me that it is one of them [the nights], for only twenty-nine nights have passed." The Messenger of Allah, peace and blessings of Allah be upon him, said: "O ‘Aishah, the month is twenty-nine."