What is the ruling on a congregational prayer in which the Imam rose from the first prostration saying, "Allah hears the one who praises Him," whereupon the worshippers said, "Our Lord, and to You be the praise," and then the Imam completed his second prostration without prostrating for forgetfulness?

The prayer of the aforementioned Imam, who recited the prescribed remembrance in the wrong place, is valid. The issue of prostration of forgetfulness (sujud as-sahw) in this case is a matter of scholarly disagreement. As for the congregant (ma'mum) who said, "Our Lord, and to You be praise" (Rabbana wa lakal-hamd) in the wrong place, there is no prostration due upon him, because the Imam bears the responsibility for his prostration of forgetfulness, according to the view that it is prescribed. Therefore, the prayer of everyone is valid.