At that time, all Jews were waiting for the prophesied Messiah. Therefore, they knew well about “the Law and the sacrificial system,” which God had given through Moses, more than any other people. They believed that the Messiah would come according to the atoning Law of God, and would free them from all their sins.
However, they did not believe that the baptism of Jesus by John the Baptist was from God and was supposed to put all the sins of the world onto Jesus (Mark 11:27-33), but rather, they considered Him as a man who led the people astray and thus, crucified Him.
Since Romans were protected from being scourged or crucified according to Roman law (Acts 22:25-29, 23:27), we see that the thieves on the Cross were not Romans, but Jews. We also see that the thief was a Jew who feared God from his words, saying, “Lord, remember me when You come into Your kingdom” (Luke 23:42). The Jewish thief already knew the Law and the sacrificial system, which God gave to Moses. So he believed that the Messiah would come according to the atoning law of God.
Those who come to God must confess that they are sinners, destined to go to hell for their sins. The thief confessed his sins, saying, “And we indeed justly, for we receive the due reward of our deeds” (Luke 23:41). We can also see that the thief feared God and his hope was to enter the Kingdom of Heaven from his words, saying, “Lord, remember me when You come into Your kingdom” (Luke 23:42).
He said, “But this Man has done nothing wrong” (Luke 23:41). What did the thief know about what Jesus did? He believed that Jesus was conceived by the Holy Spirit, was born of the Virgin Mary, was baptized by John the Baptist, the representative of all mankind, took away all the sins of the world, and was crucified. He was a Jew who believed what Jesus did for all the people, including him, even though he was crucified to receive the due reward of his deeds on earth.
Those who confessed their sins through the baptism of John acknowledged God’s righteousness when they heard all their sins would be passed onto Jesus through His baptism. However, those who didn’t receive John’s baptism of repentance rejected the will of God because they didn’t believe in Jesus’ baptism, either (Luke 7:28-30).
On the contrary, the thief who was saved confessed that everything Jesus did was correct and righteous, while the other Jews did not. He may have been one of the Jews who had heard all those things, which have been fulfilled among them (Luke 1:1). He could at last say that Jesus was righteous and the prophesied Messiah because he finally came to believe on the Cross that Jesus took away all his sins through His baptism. Accordingly, he was saved. He was also saved by believing in the gospel of the water and the Spirit.
Because God is just, He justifies those who believe in the baptism of Jesus and the Cross according to His law of the Spirit of life.