“What must I do?”
If you hinge it on what you must do…you must do it all and do it perfectly. You must keep the law to every dot and iota.
The old order is over anyway. The book (the law) has been closed. As closed as every hardened heart.
“It was because your hearts were hard that Moses wrote you this law,” Jesus replied.
The law hinged on separation. That’s why Christ uses the illustration of divorce for his narrative. What God has joined together let no man separate. We are one flesh. But religion (man made) attempts to sever us from this reality.
With mans attempts, Union is impossible but with God it is a done deal. And it is a done deal; he has given us a new heart and put a new spirit within us.