The commandment in the NT is to love God and love one another. It in this that we are to perfect and get better at. When we love as God loves we will be perfect as He is perfect.
Matthew 5:46-48 "For if you love those who love you, what reward have you? Do not even the tax collectors do the same? "And if you greet your brethren only, what do you do more than others? Do not even the tax collectors do so? "Therefore you shall be perfect, just as your Father in heaven is perfect.
This is not a new commandment, but rather, one that God has been saying from the begining.
1 John 2:7-8 Dear brothers, I am not writing out a new rule for you to obey, for it is an old one you have always had, right from the start. You have heard it all before. Yet it is always new, and works for you just as it did for Christ; and as we obey this commandment, to love one another, the darkness in our lives disappears and the new light of life in Christ shines in.
When we truly begin to perfect our love we will know the abundant life and people will begin to see it in us.
It seems to me that the whole theme of the NT is relationship founded on and directed from the words of Jesus.
Matthew 17:5 While he was still speaking, behold, a bright cloud overshadowed them; and suddenly a voice came out of the cloud, saying, "This is My beloved Son, in whom I am well pleased. Hear Him!''
Jesus taught the spirit of the law. The spirit of the law is love from a pure conscience.
1 Timothy 1:5-7 Now the purpose of the commandment is love from a pure heart, from a good conscience, and from sincere faith, from which some, having strayed, have turned aside to idle talk, desiring to be teachers of the law, understanding neither what they say nor the things which they affirm.
Keeping the spirit of the law will manifest itself in not do's and don'ts, but rather, in our relationships with others. Listen to how John speaks of not sinning and practicing righteousness.
1 John 3:9 Whoever has been born of God does not sin, for His seed remains in him; and he cannot sin, because he has been born of God.
Whoever is born of God cannot sin. In the NT what does this look like? John tells us in the following verses.
1 John 3:10-12 In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor is he who does not love his brother. For this is the message that you heard from the beginning, that we should love one another, not as Cain who was of the wicked one and murdered his brother. And why did he murder him? Because his works were evil and his brother's righteous.
I have always found this very interesting that the first murder in the Bible was commited because of the way someone worshiped.
Keeping the Sabbath should be and must be because we love God and if it is, who cares what others do. Why do I say, who cares what others do, because if they don't love God and desire to remember the Sabbath then it doesn't matter if they keep the Sabbath or not and if they love God they won't do as Cain did.