In the law it is written, With men of other tongues and other lips will I speak unto this people; and yet for all that will they not hear me, saith the Lord.
In the Law - the whole Old Testament, all being the law of God (cf. the Psalms cited as the "Law," John 10:34). The Quotation is from Isaiah 28:11-12, where God virtually saith of Israel, 'This people hear me not, though I speak to them in their familiar language: I will therefore speak to them in other tongues, those of the foes whom I will send against them; but even then they will not hearken to me;' which Paul thus applies, 'Ye see, it is a penalty to be associated with men of a strange tongue, yet ye impose this on the Church by abusing, the tongues, instead of using them intelligibly.' They who speak in foreign tongues speak like "children" just "weaned from the milk" (Isaiah 28:9), "with stammering lips," unintelligibly to the hearers, appearing ridiculous (Isaiah 28:14), or as babbling drunkards (Acts 2:13) or madmen (1 Corinthians 14:23).