If Jesus were not both God and man his work could not have eternal and personal significance for us. Because of God’s perfect justice our sins required the penalty of our death. Any sacrifice on our behalf had to be human and it had to be without blemish (sinless). No human being qualified so we were on the highway straight to hell.
The only alternative to save us was for God Himself to set aside His crown and come to earth in the flesh to die on the cross in our place because only God was worthy. A merciful God loved us that much. If Jesus had not been fully God, He could not qualify to be our Savior from sin. If Jesus had not been fully man, He could not qualify to be a sacrifice for us in the first place. The Christian faith is based on this promise.
Philippians 2:9-11 – Therefore God exalted Him to the highest place and gave Him the name that is above every name, that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus is Lord, to the glory of God the Father.
Hebrews 10:10 – By that will we have been sanctified through the offering of the body of Jesus Christ once for all.
Who is Jesus Christ? He had the very nature of God. He made Himself nothing. He humbled Himself. He became obedient to death. He even went to death on a cross. Jesus’ perfect life was a necessity. It qualified Jesus to be the sacrificial offering for our sin. The life of Jesus rendered perfect obedience to God. By being obedient to God unto death Jesus qualified as our High Priest and Mediator before God enthroned at the right hand of God forevermore.
Romans 5:19 – For as by one man’s disobedience many were made sinners, so also by one Man’s obedience many will be made righteous.
Hebrews 2:17 – Therefore, in all things He had to be made like His brethren, that He might be a merciful and faithful High Priest in things pertaining to God, to make propitiation for the sins of the people.