Musannaf Ibn Abi Shaybah 2654 — A man who enters while the people are

Uthman bin al-Aswad said: Amr bin Tamim and I entered the mosque. The imam bowed, so he and I also bowed, and the two of us walked in the state of bowing until we joined the row. When we had completed the prayer, Amr said to me: "From whom did you hear about what you did just now?" I said: "From Mujahid." He said: "I have seen Sayyiduna Ibn al-Zubayr (may Allah be pleased with him) do this."