Acts 18:8
And Crispus, the chief ruler of the synagogue, believed on the Lord with all his house; and many of the Corinthians hearing believed, and were baptized.
What this passage establishes
Corinthians heard, believed, and were baptized in a repeated apostolic pattern.
Why it matters in the argument
The apostolic record consistently treats repentance, water baptism, and Spirit reception as the commanded response to the gospel rather than optional religious accessories.
Apostolic connection
The singular name of Matthew 28:19 is enacted throughout Acts by baptism in the name of Jesus Christ, the revealed saving name.
Common misunderstanding
Baptism does not earn grace. It is a faith-response in which the believer obeys Christ, identifies with His death and burial, and calls on His name.
How to use it in conversation
Read the command, then show the apostles carrying it out. Let Acts interpret how Matthew 28:19 was understood.