and the Messenger of Allah, peace and blessings be upon him, said, “Does not one of you fear that, if he lifts his head before the imam, Allah might turn his head into the head of a donkey or remake his face into the likeness of a donkey?!” Agreed upon. Whoever steps ahead of his imam, then, is like a donkey that understands nothing of what is intended by its action, and whoever does so deserves punishment.
In another authentic hadith: “The imam has only been appointed to be followed, so do not bow until he bows and do not prostrate until he prostrates.”
Imam Ahmad and Abu Dawud relate: “The imam has only been appointed to be followed; when he bows, then bow—and do not bow until he bows; and when he prostrates, then prostrate—and do not prostrate until he prostrates.”
The Companions behind the Prophet, peace and blessings be upon him, would not bend their backs until the Messenger of Allah had gone all the way down into prostration; only after he was fully in prostration would they follow him.
When ʿUmar—may Allah be pleased with him—saw a man racing ahead of the imam, he struck him and said, “You have neither prayed on your own nor followed your imam.”