Does the prayer become void if the worshiper rises from bowing before the Imam, then realizes the mistake and returns to bowing?

Following the Imam is obligatory. For the worshiper to raise his head before the Imam is a grave sin, and it is feared that Allah may turn his head into the head of a donkey. If the worshiper precedes the Imam in a minor pillar, such as bowing or similar, without raising his head before the Imam bows, then his prayer is valid and he is not required to repeat it. However, he must repent and not return to such an act. It is recommended for the worshiper to return to follow the Imam if he has preceded him.