Acts 8:12
But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
What this passage establishes
Samaritan men and women believed the gospel and were baptized.
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.