Musannaf Ibn Abi Shayba 3:255

Ibn Idris narrated to us, from Ubayd Allah, from al-Qasim, and from Hisham, from al-Hasan, they both said regarding the man who enters the mosque while the people have already bowed: They both said: If he thinks that he will reach the people before they raise their heads, then let him bow, then let him walk until he enters the row.