Musnad Ahmad 928:16

Yazid ibn Harun narrated to us, Sufyan ibn Sa'id informed us, from 'Asim, from Zirr, who said: My father said to me: "It is the night of the twenty-seventh, and it is indeed it, without exception, by the sign which the Messenger of Allah, may Allah bless him and grant him peace, told us. So we calculated and we counted, and it is indeed it, without exception."