Many have sought to answer the question of whether the thief was a Jew or a gentile (non-Jew). It may seem at first glance to be somewhat of an irrelevancy, but it turns out to have great significance. To the question then: was the thief a Jew? At the feast it had become tradition for the governor, who constantly sought to placate the rebellious Jews, to release a Jewish prisoner to them. When Pilate asked the crowd of Jews that was gathered before him, he only lists two prisoners, Jesus and Barabbas (Mt 27:15-16). The absence of either thief from Pilate’s offer is quite remarkable if there were, in fact, Jews. Barabbas was a murderer: surely, the crowd would desire to release a thief rather than a murderer? The absence of the thieves from the governor’s offer is confirmation of what we must have already surmised–the thieves were both gentiles.
Why is it so important that the thief on the cross was a gentile? If the thief on the cross was not a gentile, then we know that the circumcision made with had was not in the thief–he had never been circumcised. We also know that when the thief came to the Lord Jesus with his petition that afterwards he did not have any opportunity to be circumcised because the entirety of his walk as a Christian would be lived out on the tree. Therefore, we conclude that circumcision does not confer the grace of God to any man in and of itself.
Thomas Aquinas teaches that original sin is remitted in circumcision (ST III 70). His position quite plainly instructs that the work of circumcision indeed transmits grace ex opere operato. Insofar as anyone accepts the writing of Thomas Aquinas, they teach that circumcision is a Sacrament. How can it be, then, that Paul, not one or twice, but three times, says that circumcision is nothing (1 Cor 7:19, Rom 2:25-29, Gal 5:3)? If circumcision imparts salvation by grace, then we could hardly accept what Paul is teaching in Corinthians or Romans or Galatians! The thief on the cross helps us to see clearly again: he was uncircumcised and was not able to accomplish circumcision before he went to be with the Lord in Paradise. This confirms for us what the Apostles taught in Acts when a dispute arose concerning circumcision (Acts 15:5). A certain sect claimed that it was necessary to be circumcised to be saved by Jesus. The conclusion of the matter is that a letter to all the churches reads thus: “we gave no such commandment” (Acts 15:24).