For. Yea, verily. Taking the words out of their own taunting lips, and turning them against themselves. Quoted in 1 Corinthians 14:21.
stammering. jabbering.
another. foreign. Referring to the Assyrian language they were (alas!) soon to hear (Compare Isaiah 33:19; Deuteronomy 28:49).
He speak: i.e. by the Assyrians.