1 Corinthians 9: 21 speaks of being “under the law of Christ,” and Galatians 6:2 speaks of “fulfilling the law of Christ.”
To live under the LAW simply means to do your best out of true sincerity, to live a godly life that is pleasing to the Lord. The problem is that living under the law requires perfect performance because the law is perfect. There are only 2 kinds of grades that can be given to those who want to live under the law, A+ or F, and nothing in between. The good news is that when we were crucified with Christ, we did not just die to sin; we also died to the law. We are no longer required to do our best for God out of sheer sincerity if we have now been united with the life of another whose life is always pleasing to the Father. To live under the “law of Christ,” or to fulfill the law of Christ is to simply live the Christian life by His life and His ethics. His life looks like love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control. Galatians 5:23 says, “against such things, there is no law.” In other words, there is no need for the external standard to make demands on us when we are manifesting the life and ethics of Christ. James 1:25 says, “But one who looks intently at the perfect law, the law of liberty, and abides by it, not having become a forgetful hearer, but an effectual doer, this man shall be blessed in what he does.” The law of liberty that we are to intently look at and to is the very life of Christ within. One more verse is very enlightening: Romans 8:2, 4, “For the law of the Spirit of life in Christ Jesus has set you free from the law of sin and death. In order that the righteousness of the law might be fulfilled in us, who do not walk according to the flesh (trying our best to be pleasing to God in our own strength keeping external laws) but according to the Spirit.” Because we are now in Christ, we live by the law of His life, and that law of the Spirit of Life in Christ Jesus sets us free from the futility of religious self-effort. It is a law of life, and that law of life is His life, and His life results in righteousness being fulfilled in us by Him and not by us for Him. Oh, the glorious freedom of those in Christ Jesus.