What is the ruling on the prayer of someone who joined the Imam in the third rak'ah, and when he was reciting Al-Fatihah, the Imam bowed, so he completed it and bowed, but the Imam rose from bowing before the worshipper bowed? Is his prayer valid?

Scholars have differed concerning the ruling on a congregant whose Imam bows before the congregant completes Al-Fatiha. The majority opinion is that the congregant bows, following their Imam. However, the Shafi'is hold that the congregant completes Al-Fatiha even if the Imam precedes them. According to the Shafi'i view, if the congregant intentionally omits any part of Al-Fatiha while knowing the ruling, their prayer is invalidated. But if they complete Al-Fatiha before bowing, their prayer is valid.