Musannaf Ibn Abi Shayba 3:4976

Waki’ narrated to us, Talha bin Yahya narrated to us, he said: I heard Ubayd Allah bin Abdullah bin Utbah, from Umm Salamah, she said: The Prophet, peace and blessings of Allah be upon him, was kept busy from the two rak'ahs after Dhuhr, so he prayed them after Asr.