who gave Himself for our sins so that He might rescue us from this present evil age, according to the will of our God and Father,Galatians 1:4(NASB)
Paul was not ashamed of the gospel of Christ for he knew that it is the power of God unto salvation for all who believe. Paul received revelation of the gospel of grace directly from God - not from the twelve apostles or from any other eye-witnesses of Christ's earthly life.
But just as it is today, there were those in Paul's time who questioned his authority because he did not receive the gospel he taught from Christ's apostles. As a consequence, they held fast to some pre-Cross legalism rather than accepting the post-Cross gospel of grace which was delivered to Paul by direct revelation from the risen and glorified Christ. Even Peter and the other disciples had to be delivered from some pre-Cross legalism that they were holding onto.
The gospel of Paul was received directly from God and was centred upon the death, burial, and Resurrection of Christ. Paul's gospel was the gospel of peace-with-God through salvation and the peace-of-God residing within the believer. It was the gospel (good news) of salvation by grace through faith in Christ (justification) and it was the gospel (good news) of life and liberty in Christ (sanctification) and not the legalistic bondage suffered under the Law and the curse that brings in it wake.
The gospel of Paul was focused on Christ: "Who gave Himself for our sins so that He might rescue us from this present evil age, according to the will of our God and Father." The perfect standard of the Law certainly points us to Christ, Who alone was able to fulfil the righteous requirements of the Law on our account. It was the Lord Jesus, Himself, Who took it upon Himself to fulfil the Law on our behalf - and then He identified with our sinfulness so that He, Himself, could pay the price for your sin and mine.
He fulfilled the Law on our behalf so that by faith in His finished work we might be redeemed from the curse of the Law, which is death. Christ gave Himself for our sins because there was no other way to rescue us from this present evil age and the power of death over us. The Law may be able to identify our sins and condemn us as guilty sinners - but the Law can never save us from our sins but leaves every one guilty as charged.
Jesus gave His life for our sins in order to save us from this evil world in which we live - so that we might be liberated from the unbearable burden of knowing that we are sinners while being incapable of doing anything about it - knowing that our sin separates us from God, but not being able to do anything to help ourselves.
But Christ gave Himself for us because this was the will of the Father in heaven Who loved the world so much, He gave His only begotten Son so that whoever believes in Him, might be rescued from this evil age and have life everlasting.
Christ, the eternal Son of God, died on the Cross and rose again the third day to be the propitiation for our sins in order to satisfy the righteous requirement of a holy God Who was eternally separated from the human race by sin but Who, before the foundation of the world, planned and purposed (by His perfect will) to give Himself for our sin so that He might rescue us from this present evil age and the power of death.
Heavenly Father, thank You that in Your grace and wisdom, Christ gave Himself for my sins and for the sins of the whole world so that by grace through faith in Him, all who believe might be rescued from this present evil age. Thank You that You chose, in eternity past, to plan for the salvation of mankind, who by rights should remain guilty as charged. Praise Your holy name, AMEN.