لَمَسَخۡنَٰهُمۡsurely, We (would have) transformed themlamasakhnāhum
عَلَىٰinʿalā
مَكَانَتِهِمۡtheir placesmakānatihim
فَمَاthen notfamā
ٱسۡتَطَٰعُواْthey would have been ableis'taṭāʿū
مُضِيّٗاto proceedmuḍiyyan
وَلَاand notwalā
يَرۡجِعُونَreturnyarjiʿūna
Tafsir
If I had willed to alter their form and make them sit on their feet I would have altered their form and made them sit on their feet, and they will not be able to move from their place nor will they be able to move forward nor backward.