What is the ruling on the Imam or the congregant saying "Our Lord, and to You be praise" after "Allah hears whoever praises Him"? And does that invalidate the prayer? And what is the ruling on saying "Allah hears whoever praises Him" and "Our Lord, and to You be praise"? And is it obligatory, Sunnah, or desirable? And what are the consequences of omitting it due to forgetfulness or intentionally?

It is prescribed for the Imam to say: "Sami'allahu liman hamidah" (Allah hears those who praise Him), and then "Rabbana wa lakal hamd" (Our Lord, to You be all praise) upon rising from bowing. As for the congregant (ma'mum), according to the majority of scholars, he only says: "Rabbana wa lakal hamd." Both are considered Sunnah by the majority of scholars, and obligatory according to the Hanbalis. Whoever intentionally omits them, holding the view that they are Sunnah, his prayer is valid. Whoever intentionally omits them, holding the view that they are obligatory, his prayer is invalid. Whoever omits them forgetfully, they are compensated for by the prostration of forgetfulness (sujood as-sahw).