1 Peter 1:18-23  Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers;  But with the precious blood of Christ, as of a lamb without blemish and without spot:  Who verily was foreordained before the foundation of the world, but was manifest in these last times for you, Who by him do believe in God, that raised him up from the dead, and gave him glory; that your faith and hope might be in God.  Seeing ye have purified your souls in obeying the truth through the Spirit to unfeigned love of the brethren, see that ye love one another with a pure heart fervently: Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth forever. 

We have been redeemed by the blood of Jesus. It was necessary that a man, Jesus, obey the Father and never obey Satan and that that man, Jesus, would obey to death. It was necessary that God come to earth in the form of a man so that God Himself could become the sacrifice for sin. No man would be adequate for the task, No mere man could possibly obey God in every point. That would take the God-man, Jesus.