But they held their peace... — Hezekiah seems to have commanded silence, as if distrustful either of the wisdom of the ambassadors or of the effect which any chance words might have upon the garrison and people of Jerusalem. As it was, the only words they had spoken (Isaiah 36:11) had made matters infinitely worse.
Related Commentaries of Isaiah 36:21
Isaiah 36:21
21 But they held their peace, and answered him not a word: for the king's commandment was, saying, Answer him not.