“… I am writing a new commandment to you, which is true in Him and in you, because the darkness is passing away and the true Light is already shining.” (1 John 2:8) The new commandment is “the law of love.” The Law (1st Covenant) proved we couldn’t live up to what was required by God in and of ourselves. “Therefore the Law has become our tutor to lead us to Christ, so that we may be justified by faith.” (Galatians 3:24)
The solution to our human condition was that the Father sent His Son to pay the price for our sin. Therefore, the law is now manifestly not the path to righteousness; Christ is. The ultimate goal of the law is that we would look to Christ, not law-keeping, for our righteousness.
So now if we walk in the light, we can love one another. With Christ, the bar has been raised. More is expected. We are to fulfill the Law. We can if we continue to walk in the light. If we hate our brother, we are walking in darkness. Darkness has no fellowship with light.