Tafsir of Al-Anbiya' 21:65

ثم نكسوا على رووسهم

Then they turned to themselves, means, they looked at the ground, and said:

لقد علمت ما هوﻻء ينطقون

Indeed you (Ibrahim) know well that these speak not! Qatadah said: "The people admitted their guilt and confusion, and said,

لقد علمت ما هوﻻء ينطقون

("Indeed you know well that these speak not!'') `So how can you tell us to ask them, if they cannot speak and you know that they cannot speak.' At this point, when they admitted that, Ibrahim said to them:

قال أفتعبدون من دون الله ما ﻻ ينفعكم شييا وﻻ يضركم