An orthodox understanding of the deity of Christ compels us to say he could not have failed in his mission. Indeed, if he could have failed, he is not all powerful and therefore he was not and is not God.
True, as Philippians 2 shows (and is illustrated by the Son “doesn’t know the hour”), Jesus chose to lay aside the exercise of some of his divine prerogatives, but never did he divest himself of his attributes. So, yes, Jesus could hunger and thirst as a man, but there is no moral imperfection in hunger and thirst. He could not sin, because that would have not been a choice not to exercise a power, but would have been a violation of his essential nature. God can choose to make himself hungry, but he cannot choose to make himself sin.
If Jesus could sin, and Jesus is God, then God can sin. If Jesus could fail, and Jesus is God, then God can fail. If God could have failed during the incarnation of Christ, why not at other times? Can we really count on him? Scripture says in him there is no shadow of turning or change. Jesus Christ is the same yesterday, today and forever. If Jesus could have failed yesterday, then he could fail today and in the future.
Is appealing to Christ’s deity to say he could not fail a form of cheating? No. In his temptation, Jesus refused to rely on his divine ability to change the stone into bread, and thereby make obedience easier. His divine nature is a “backstop” that would prevent him from sinning, but he was still truly facing temptations. Does this mean the temptations weren’t real? Of course not. Grudem uses the analogy of a weightlifter who successfully lifts and holds the heaviest weight ever lifted. Would we say he can’t relate to all those people who tried to lift without success? No, the weight falls hardest on the one who actually lifts the most. We could better argue that the rest of us don’t understand what it’s really like to resist sin, because we cave into it. Jesus really understands. Arguably, Christ’s temptations were more real precisely because he didn’t yield to them, and that is not diminished by the fact that he couldn’t. His divine attributes made it harder for him on the cross, since it brought his total holiness under the judgment of sin—he became sin for us (2 Corinthians 5:21).
Taken from "Could Jesus have failed in His mission to redeem us?" by Randy Alcorn, Eternal Perspective Ministries, 39085 Pioneer Blvd., Suite 206, Sandy, OR 97055, 503-668-5200, www.epm.org