What is the ruling on the mistake of the worshipper in congregational prayer when the prayer of the Imam is sound?

The mistakes of the worshiper (ma'mum) that invalidate the prayer, such as omitting a pillar (rukn) or a rak'ah (unit of prayer), are not borne by the imam. The worshiper must rectify these before their time elapses. As for mistakes that do not invalidate the prayer, such as omitting supererogatory acts (mustahabbat) and sunnahs, these are borne by the imam.