1 Corinthians 14:2 says tongues are for God, not men — a private use, contrasting the public judgment sign here.

1 Corinthians 14:11 illustrates the foreigner concept — if language is unknown, speaker is a barbarian, echoing the judgment imagery.

Deuteronomy 28:49 describes a foreign nation with an unknown tongue as a covenant curse — the same judgment principle Paul quotes here.

Isaiah 28:11 is the direct source of Paul's quote — God speaks through stammering lips as a sign of judgment.

Isaiah 28:12 continues the quote — the people refused to listen, which Paul includes as 'yet they will not hear me'.

Jeremiah 5:15 also warns of a nation whose language you do not know — a parallel prophecy of judgment by foreign tongues.

In Acts 2:4, tongues enable proclamation to all nations — a positive sign, contrasting the judgment sign in Paul's quote.

Isaiah 33:19 describes a people of obscure speech — another OT image of foreign tongues as a sign of judgment.