Christology is an inexhaustible subject. Concerning His incarnation alone, the apostle John said, “There are also many other things which Jesus did, which if they were written in detail, I suppose that even the world itself would not contain the books that would be written” (John 21:25).
We cannot know everything about Christ. But we can know everything we need to know in order to receive His mercy and inherit eternal life. And for that, we don’t need to study systematic theology or evangelistic methodology. The answers come from a criminal during a brief cameo in the gospel of Luke.
One of the criminals who were hanged there was hurling abuse at Him, saying, “Are You not the Christ? Save Yourself and us!” But the other answered, and rebuking him said, “Do you not even fear God, since you are under the same sentence of condemnation? And we indeed are suffering justly, for we are receiving what we deserve for our deeds; but this man has done nothing wrong.” And he was saying, “Jesus, remember me when You come in Your kingdom!” And He said to him, “Truly I say to you, today you shall be with Me in Paradise.” (Luke 23:39–43, emphasis added)
Five critical aspects of the thief’s Christology are revealed in verses 41 and 42.
The Thief Declared Christ’s Righteousness
The thief knew crucifixion was deserved, so far as he was concerned. He described his slow torturous death as “suffering justly” and “what [he] deserved for [his] deeds” (Luke 23:41). But concerning the Man on the cross next to him, the thief declared that “this man has done nothing wrong.” Christ’s perfect righteousness shone into the dark recesses of a man whose life was marked by wickedness. John MacArthur comments:
The final evidence of the repentant thief’s divinely transformed heart was his belief in Jesus Christ. The story of his transformation moves from an assessment of his sinful condition to an assessment of the Savior’s character. When he said of Him, “This man has done nothing wrong,” he was confessing not merely the Lord’s innocence of any crime, but also His sinlessness.  John MacArthur, The MacArthur New Testament Commentary: Luke 18–24 (Chicago: Moody Publishers, 2014), 387.
The apostle Paul recognized the necessity of Christ’s sinlessness in order for Him to be our sin-bearing substitute: “He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him” (2 Corinthians 5:21).
The Thief Appealed to Christ Exclusively
It should not escape our notice that the thief never made his plea for mercy to the powers visibly present around him. At the foot of the cross stood representatives of Roman political power as well as members of Israel’s religious elite. But the thief made no appeal to the Romans for exoneration, nor to the Jews for spiritual absolution. Mustering what little remained of his strength and consciousness, the thief made his only appeal to the crucified Savior.
The exclusivity of Christ is a central tenet of the Christian faith. Jesus made it clear that He is the way—not a way—to heaven (John 14:6). The apostles continued that message as they established the early church, stating that “there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved” (Acts 4:12). Christ grouped every other religion into one doomed category, and consequently, His exclusive claims are offensive to many. But the thief, in his most desperate hour, knew Jesus was his only hope.
The Thief Requested Christ’s Forgiveness
The thief was not confused about his most desperate need. John MacArthur points out that the thief’s request for Jesus to remember him was synonymous with a cry for pardon.
He then addressed Jesus directly as the Savior and humbly asked Him, “Jesus, remember me when You come in Your kingdom!” This was nothing less than a plea for the forgiveness apart from which no one will enter God’s kingdom. He based his request on Christ’s prayer that God would forgive those who crucified Him, which gave him hope that he too might receive forgiveness. He expressed belief that Jesus is the Savior, since he would not have asked for entrance to the kingdom unless he believed Jesus was willing and able to provide it. His was the plea of a broken, penitent, unworthy sinner for grace, mercy, and forgiveness.  MacArthur, The MacArthur New Testament Commentary: Luke 18–24, 387.
The thief’s subjective feelings and painful circumstances were not the focus of his plea to Christ. Instead, he knew what his true and ultimate need was—forgiveness.
The Thief Recognized Christ’s Authority
Implicit in the thief’s plea for forgiveness was his recognition of Christ’s authority to grant forgiveness and eternal life.
The thief also knew who the real King was at Calvary, since he ascribed God’s kingdom as “Your kingdom” (Luke 23:42).
He believed that Jesus was Israel’s Messiah. He acknowledged that the Lord would one day establish His kingdom, which was promised in the covenants God made with Abraham and David, and reiterated repeatedly to the prophets.  MacArthur, The MacArthur New Testament Commentary: Luke 18–24, 387–88.
The Thief Anticipated Christ’s Resurrection
The gospel narratives don’t shy away from exposing the unbelief of Christ’s closest disciples. All of them barring John fled at His arrest and despaired of His death—even though Jesus taught them repeatedly that He would rise from the dead. There is only one character in the gospel narratives who demonstrates authentic belief in Christ’s coming resurrection—and that’s the thief.
Even the casual reader of Scripture can’t help but be amazed at the thief’s preoccupation with eternal matters. Rather than be overwhelmed with the doom of a Roman cross, he was able to unmistakably articulate his confidence that Christ would soon rise from the dead. Moreover, as John MacArthur explains, he based his own hope of personal resurrection on the reality of Christ’s coming resurrection.
Since no one survived crucifixion, he understood that Jesus would have to rise from the dead to do that. He probably knew that Jesus had power over death, since the news of His raising of Lazarus had spread throughout Jerusalem. He no doubt was aware that Daniel 12:2 promised that the saints would be raised and given a place of glory in the kingdom. His request was that Jesus would raise him and grant him entrance to that kingdom.  MacArthur, The MacArthur New Testament Commentary: Luke 18–24, 388.
Through the pain of crucifixion, the thief was still able to declare Christ’s righteousness, appeal to Him exclusively, petition His forgiveness, recognize His authority, and anticipate His future resurrection. In all, the thief spoke six words about Christ and nine words to Christ. Those two brief statements reveal a man with an outstanding grasp of Christology.
There is a profound simplicity to the thief’s faith in the Savior. And it is a glorious benchmark for every sinner who approaches Christ in repentance and faith.