Musannaf Ibn Abi Shayba 3:3769

Abu Bakr narrated to us, he said: Abbad bin al-Awwam narrated to us, from Abd al-Malik, from Ata, regarding a man who enters the mosque while the row is complete: He said: If he is able to enter into the row, he enters. Otherwise, he takes a man by the hand and makes him stand with him, and he does not stand alone.