This story reveals the truth to us that salvation is conditioned upon repentance and faith. However, it contains other important messages also. It declares that salvation is independent of sacraments. The thief had never been baptized, nor had he partaken of the Lord’s Supper. ... He did in fact boldly profess his faith in the presence of a hostile crowd and amid the taunts and jeers of rulers and soldiers, yet he was saved without any formal rites. It is further evident that salvation is independent of good works. ... It is also seen that there is no “sleep of the soul.” The body may sleep, but consciousness exists after death. Again it is evident that there is no “purgatory.” Out of a life of sin and shame, the penitent robber passed immediately into a state of blessedness. Again it may be remarked that salvation is not universal. There were two robbers; only one was saved. Last of all it may be noted that the very essence of the joy which lies beyond death consists in personal communion with Christ. The heart of the promise to the dying thief was this: “Thou shalt be with me.” This is our blessed assurance, that to depart is “to be with Christ” which is “very far better.”
Charles R. Erdman, The Gospel of Luke, pp. 217,218. Cited by William MacDonald in The Believer’s Bible Commentary.