What is the ruling on adding the word "wal-shukr (and thanksgiving)" after saying "Rabbana wa lakal-hamd (Our Lord, to You be all praise)"?

Adhering to the narrated remembrances (adhkar) is best. So, upon rising from genuflection (ruku'), one should say: "Rabbana wa lakal-hamd" (Our Lord, and to You be all praise), without adding "wash-shukr" (and thanks), as it has not been reported.

There are four reported forms for rising from genuflection: "Rabbana wa lakal-hamd" (Our Lord, and to You be all praise), "Rabbana lakal-hamd" (Our Lord, to You be all praise), "Allahumma Rabbana lakal-hamd" (O Allah, our Lord, to You be all praise), and "Allahumma Rabbana wa lakal-hamd" (O Allah, our Lord, and to You be all praise). These forms are recited alternately, not all in a single prayer.