Musannaf Ibn Abi Shayba 3:226

Abu Bakr narrated to us, he said: Abd al-A’la narrated to us, from Ma’mar, from al-Zuhri, from Salim, from Ibn Umar and Zayd ibn Thabit, they said: If he finds them having raised their heads from the bowing (ruku’), he should say the takbir and prostrate, and he should not count it (as a rak’ah).