I don't think there is any scripture telling us we must choose only one, but as Paul tells us when he explains grace to us "heaven forbid". We are to know about grace, and we are to know about law.
Paul speaks against legalistic obedience even calling this sort of obedience the law of Moses. At that time many gentiles were only temporarily joining God's people then leaving taking their Jewish friends they made with them. The chief rabbis decided to make many rules for joining them and the word in the street about it was to call these requirements the law of Moses. Paul spoke against this, but there is never any scripture about a requirement not to keep God's laws.
Paul tells us that it is impossible for humans to keep God's law perfectly, that we are not perfect and can't be perfect. Humans are fond of saying that if they can't do it all they won't do any of it, but that is not scripture.
We are told to obey law, and we are told this obedience is not looked at by the Lord to decide on grace for us. Our faith is what God sees. The two, in scripture, are entirely separate. But each of the two, grace and law, are to be understood by us.
God want us to chose grace. Because we are not able to produce or do the law, when we chose grace than that grace Will help us to do the law of love.
Back to John 15
4 Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
5 I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing.
6 If a man abide not in me, he is cast forth as a branch, and is withered; and men gather them, and cast them into the fire, and they are burned.
Jesus say branch can not bear the fruit of itself.
Fruit of the Holy spirit is love
Love is the spirit of law
Matt 22
37 Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.
38 This is the first and great commandment.
39 And the second is like unto it, Thou shalt love thy neighbour as thyself.
40 On these two commandments hang all the law and the prophets.
So when we do love we do the law.
Do not steal > when we love a person we not steal from, instead we give something to that person.
Can we chose to do the law?
We may not steal, can we do love, pure love?
Not without grace. Jesus say the branch can not bear the fruit of itself.
So do not chose law because It is not a choice. You don't have ability to chose do the law.
Chose grace than Jesus do the law through you, not that you have ability to do the law, but Jesus in you
You No longer yourself but Jesus in you
Galatians 2
19 For I through the law died to the law that I might live to God. 20 I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me. 21 I do not set aside the grace of God; for if righteousness comes through the law, then Christ died [a]in vain.”
NO LONGER I WHO LIVE! BUT CHRIST LIVES IN ME
Who chose to do the law?
Is that you?
How you chose when you die, you No longer live.
Can death person do the law?
Can death person chose something?
Logically speaking, If a person against the law, It mean he still a live, Jesus not live in him yet
I believe we are oN and off, some time we let Jesus live in us, and we die, some time we ask Jesus to go and we want to live for ourself.
Chose a grace do not mean chose against the law of love.
Chose a grace mean chose to die and let Jesus live oN us.