It is by a perfect law that we are saved; else it would be an unholy salvation. It is by a perfect law fulfilled in "every jot and tittle" that we are saved; else it would be an unrighteous salvation. The Son of God has kept this law for us; He has magnified it and made it honorable; and thus we have a holy and righteous salvation. Though above law in Himself, He was made "under the law" for us; and by the vicarious law-keeping of His spotless life, as well as by endurance unto death of that law's awful penalties, we are redeemed from the curse of the law.
"Christ is the end (the fulfilling and exhausting) of the law for righteousness to everyone that believeth" (Romans 10:4).
For Christ is not a helper, but He is the Saviour. He did not come to enable us to save ourselves by keeping a mitigated law, but to keep the unmitigated law in our room, that the law might have no claim for penalty upon any sinner in Christ.