Musannaf Ibn Abi Shayba 35:33

Mulaazim ibn 'Amr narrated to us, from 'Abdullah ibn Badr, he said: 'Abdur-Rahman ibn 'Ali ibn Shayban narrated to me, from his father, 'Ali ibn Shayban—and he was among the delegation—he said: We set out until we arrived at the Prophet of Allah, may Allah bless him and grant him peace, and we pledged allegiance to him and prayed behind him. He saw a man praying behind the rows. He said: The Prophet of Allah, may Allah bless him and grant him peace, stood over him until he finished. Then he said: "Repeat your prayer, for there is no prayer for the one who is behind the row." And it was mentioned that Abu Hanifah said: His prayer is sufficient for him.