1 Corinthians 14:21

In the law] i.e. the OT. (Isaiah 28:11). As God confounded the unbelieving Jews who rejected Isaiah's plain warnings as folly, by bringing upon them invaders (Assyrians) of unintelligible speech, so tongues are meant to impress unbelievers, as a sign of the existence of spiritual influences; but, as of old, many will be confirmed by them in their unbelief.