In His humanity Christ lived a perfect and sinless life by faith in total obedience to God’s will without utilizing His own equality with God (Philippians 2:6). Therefore He is the author and perfecter of faith (Hebrews 12:2). This also removes the common excuse for our failures and sins that “we are not Jesus.” We would do well to remember that in His humanity He didn’t utilize His equality with God and was tempted in all things as we are, yet without sin (Hebrews 4:15).
The perfect and sinless life of Christ was necessary for penal substitution – so that through His death, although He didn’t deserve to die, He could make propitiation for the sins of the people. The death of Christ was not for Himself but for others – “For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, and that He was buried…” (1 Corinthians 15:3). This great and liberating truth is what we also sing about - “He took my sins and my sorrows, He made them His very own; He bore the burden to Calvary, and suffered and died alone” (I Stand Amazed in the Presence).
So the incarnation was in order to make penal substitution a possibility and the crucifixion was in order to make penal substitution an actuality. It was through the death of Christ, the sinless Son of God, as our substitute, that God could legally and justly forgive us of our sins. “He (God) made Him (Jesus) who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him” (2 Corinthians 5:21). “And He Himself bore our sins in His body on the cross, so that we might die to sin and live to righteousness; for by His wounds you were healed” (1 Peter 2:24).
However, there is more to the good news about Christ than His sinless life and sacrificial death. There is no good news if Jesus only lived a sinless life and died a sacrificial death. IF that were the case then none of us could or would be forgiven (1 Corinthians 15:17). Without the resurrection of Christ, the atonement would amount to a double injustice (Proverbs 17:15). BUT, with His resurrection, the atonement is just and God is both just and the justifier of the one who has faith in Jesus (Romans 3:26).