This is a good question that is on the mind of alot of Christians: Could Jesus have sinned? The answer hinges on the meaning of "could." The biblical answer is an emphatic "yes." Jesus could have sinned. Hebrews 2:18 says, "Because he himself has suffered when tempted, he is able to help those who are being tempted." Jesus was tempted to sin. This was part of his full humanity. Many people will say, "Since Jesus was not able to sin, he really wasn't tempted." But Jesus was able to sin and he did feel the full strength of temptation. Indeed, as often has been observed, Jesus knows more about temptation than we do, and he felt more of the pain of resisting temptation than we ever will. This is for the simple reason that long after we give in to temptation, Jesus held out. Thus the writer of Hebrews says, "For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin" (Heb. 4:15). An aspect of Jesus' full humanity is that he could sin and he also could truly suffer under temptation.
The typical reply to this teaching is, "Yes, but Jesus was also God and his nature was not corrupted by sin." These are both true, but they don't change the situation. Yes, God cannot sin. But Jesus added a true human nature to his deity. Jesus, the Son of God, was truly man, so as the Bible insists he was truly tempted to sin. Now, it was not Jesus' nature to sin -- praise the Lord for that. His was a perfect human nature, with the ability but not the desire to sin; in fact, his will was perfectly joined to the will of his Father. But that does not make Jesus any less human -- as if sinning is integral to humanness. We might say that Jesus could sin but that he would not sin.
Of course, there is mystery involved in this due to the dual natures of Christ. Jesus is one person with two natures: human and divine. We ascribe his ability to sin to his human nature and his power to defeat temptation to his divine nature. There is analogy here with Jesus' death. Jesus the person suffered death. His human nature was capable of dying, though in his divine nature he possessed indestructible life (Heb. 7:16, 24). Likewise, Jesus could sin in his true humanity and could not sin in his true deity. The weakness he embraced by becoming true man was upheld by the power of his deity. But this does not mean that his resistance to sin lacked virtue; indeed, as I said above, his resistance to temptation was more costly to him than it is to us for the simple reason that he never relented.
This brings us to a good rule of thumb. Any time we think that Jesus' deity somehow limits his humanity, we are wrong. Rather, the weakness of his humanity was upheld by the power of his deity. Being able to sin is part of humanity -- although the desire to sin is merely a corruption of true humanity -- so Jesus as true man could sin. This was part of his true human nature. But the person of Jesus would not sin because his true humanity was fortified by his true deity.
Richard Phillips is chair of the Philadelphia Conference on Reformed Theology and senior minister of Second Presbyterian Church in Greenville, SC.