Musannaf Ibn Abi Shayba 3:2764

Sufyan ibn 'Uyaynah narrated to us, from 'Amr, from Yusuf ibn Mahak, who said: Mu'adh arrived in Makkah while they were gathering [for prayer] in the Hijr. He said: "Do not gather until the Ka'bah casts its shadow from its face."