Is it obligatory for the congregant to bow immediately after the imam bows, or should he complete the recitation of the verse?

If the verse is short and the worshipper is certain he will catch the bowing with the Imam, then completing it is not considered falling behind. However, if it is long, he should cut it short and follow the Imam, based on the Prophet’s (peace be upon him) saying: “Indeed, the Imam is appointed to be followed. So, when he says ‘Allahu Akbar,’ say ‘Allahu Akbar,’ and when he bows, bow…” And it is considered falling behind without an excuse if the Imam bows and the worshipper busies himself with completing the recitation of the surah (definition) or prolongs the glorification in bowing and prostration.