Our Lord — though sinless, holy, and perfect — was crucified between two criminals, He was "numbered with the transgressors" (Is 53:12). This reminds us of what the Lord's Supper shows us: that He hung there in our place, as our Substitute. We, not Christ, are the transgressors. It should have been us hanging there on the tree between the two thieves. It should have been us suffering the shameful death of the cross. But Christ took our place. He was numbered among the transgressors in our stead.
Jesus hung between the two thieves. God used those two men to dramatize the only two possible responses to the Christ: belief and unbelief, acceptance and rejection, repentance and impenitence.