The Bible decisively teaches that, in the Christian age, immersion for the remission of sins is necessary for salvation (e.g., Acts 2:38; 22:16; Romans 6:1-4). And yet, sometimes a person will say that he wants to be saved “like the thief on the cross was saved,” meaning “without being baptized for the forgiveness of sins.” Those who follow the Lutheran doctrine of ‘salvation by faith alone,’ and thus believe that a sinner receives salvation at the moment when he believes in Jesus, often cite Luke 23:39-43 as evidence. In this text, we read:
One of the criminals who were hanged railed at him, saying, “Are you not the Christ? Save yourself and us!” But the other rebuked him, saying, “Do you not fear God, since you are under the same sentence of condemnation? And we indeed justly, for we are receiving the due reward of our deeds; but this man has done nothing wrong.” And he said, “Jesus, remember me when you come into your kingdom.” And he said to him, “Truly, I say to you, today you will be with me in Paradise.”
No one should say that the penitent thief was lost, for Christ Himself said that the thief was saved. And it is possible that the penitent, saved thief never had been baptized by Christ’s disciples or by John’s disciples. (Recall that these preparatory baptisms were exclusively for Jews, and specifically for those living around Judea [John 3:22-26; 4:1-2].)
It is essential to understand that the thief lived prior to the law or covenant of Christ coming into effect. Christ had not died yet, and so His covenant was not yet binding. The author of the book of Hebrews makes this point clearly:
Therefore [Christ] is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant. For where a will is involved, the death of the one who made it must be established. For a will takes effect only at death, since it is not in force as long as the one who made it is alive (Hebrews 9:15-17, emp. added).
Because Christ had not yet died, the thief on the cross was not amenable to the last will and testament of Christ—His new covenant. In fact, the thief could not possibly be baptized “into the death of Christ,” because Christ had not yet died (Romans 6:3-4). However, water baptism is required for those of us living in the Christian age to receive the free gift of salvation, in accordance with the Law of Christ (Galatians 6:2).