Isaiah 28:11 - Ellicott's Commentary On The Whole Bible

With stammering lips and another tongue... — The “stammering lips” are those of the Assyrian conquerors, whose speech would seem to the men of Judah as a barbarous patois. They, with their short sharp commands, would be the next utterers of Jehovah’s will to the people who would not listen to the prophet’s teaching. The description of the “stammering tongue” re-appears in Isaiah 33:19. (Comp. Deuteronomy 28:49.) In 1 Corinthians 14:21, the words are applied to the gift of “tongues,” which, in its ecstatic utterances, was unintelligible to those who heard it, and was therefore, as the speech of the barbarian conquerors was in Isaiah’s thoughts, the antithesis of true prophetic teaching.