Musannaf Ibn Abi Shayba 3:4299

Thaqafi narrated to us, from Abdullah bin Uthman, from Mujahid, who said: I went out with Ibn Umar from the house of Abdullah bin Khalid. When we looked toward the door of the mosque, the people were in the Asr prayer. He remained standing until the people finished praying. He said: "I have already prayed in the house."