ثُمَّ نُكِسُوا۟ عَلَىٰ رُءُوسِهِمْ لَقَدْ عَلِمْتَ مَا هَٰٓؤُلَآءِ يَنطِقُونَ
Important Words:
نکسوا علی رؤوسھم (their heads were made to hang low for shame). نکسوا is derived from نکس . They say نکسه or نکسه (nakkasahu) i.e. he turned it over or upside down; changed its manner of being or state; he turned it over upon its head. نکس رأسه means, he bent or lowered or hung down his head towards the ground for shame or by reason of abasement. نکس المریض means, illness returned or reverted to the sick man. نکس الرجل means, the man became weak and powerless (Lane, Aqrab & Ma‘ani). Thus the Quranic expression نکسوا علی رؤوسھم would mean, (a) they returned to their former state of disbelief, or wicked behaviour; (b) they reverted to disputation after they had taken the right course; (c) they hung down their heads in shame and were completely dumbfounded, or their heads were made to hang low for shame.
The Arabic expression may mean: (a) They returned to their former state of disbelief, or wicked behaviour; (b) they reverted to disputation after they had taken the right course; (c) they hung down their heads for shame and were completely dumbfounded (Lane & Ma‘ani).