Assalam Alaikum IhsanAllahu Alaykum Ustadh You mentioned that the minimum for Ruku is - 1) Bent Back 2) Hands on knees So if you've done these two yet you haven't said Subhana Rabbiul Adheem and you hear the س from the Imam Is your Ruku valid and that Rakah counts? Barakallahu Feekum

Ustadh AbdulAziz al-Haqqan

Ruku is valid yes and you can say once before moving up