Question: Why must the redeemer be truly God?
Answer: That because of his divine nature his obedience and suffering would be perfect and effective; and also that he would be able to bear the righteous anger of God against sin and yet overcome death.
Scripture: Acts 2:24
In order to answer the the reciprocal question regarding Jesus deity, I will once again turn to Wayne Grudem and his answer in his excellent Systematic Theology:
It is crucially important to insist on the full deity of Christ…not only because it is clearly taught in Scripture, but also because (1) only someone who is infinite God could bear the full penalty for all the sins of all those who would believe in him – any finite creature would have been incapable of bearing that penalty; (2) salvation is from the Lord (Jonah 2:9, NASB), and the whole message of Scripture is designed to show that no human being, no creature, could ever save man – only God himself could; and (3) only someone who was truly and fully God could be the one mediator between God and man (1 Tim. 2:5), both to bring us back to God and also to reveal God most fully to us (John 14:9).
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