Scripture-first response
“The thief on the cross was not baptized.”
The thief received a direct promise from Jesus before the new-covenant commission began. The risen Christ later commanded the gospel response for all nations.
What the objection is claiming
A person saved before Christ’s death and resurrection is treated as living under the post-resurrection gospel commission.
Luke 24:46-47
46 And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: 47 And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem.Open full referenceThe risen Christ defines the saving message as His death and resurrection proclaimed with repentance and remission in His name.
How the passages answer it
Christian baptism identifies the believer with Christ’s completed death and burial and belongs to the commission issued after resurrection. The thief’s promise is true, but his timing and circumstances do not cancel the commands Jesus later gave the church.