Jamieson, Fausset and Brown on Exodus 11:8

8. all these thy servants shall ... bow down themselves unto me--This would be the effect of the universal terror; the hearts of the proudest would be humbled and do reverential homage to God, in the person of His representative.

went out ... in a great anger--Holy and righteous indignation at the duplicity, repeated falsehood, and hardened impenitence of the king; and this strong emotion was stirred in the bosom of Moses, not at the ill reception given to himself, but the dishonor done to God (Mt 19:8; Ep 4:26).