Musannaf Ibn Abi Shaybah 2626 — Those who said: if you enter while

Sayyiduna Ibn Umar (may Allah be pleased with them both) and Sayyiduna Zayd bin Thabit (may Allah be pleased with him) said: If a person finds the people when they have already raised their heads from bowing, he should say "Allahu Akbar", prostrate, and not count that rak'ah.