In Christ, nobody is created or designed to be regulated, ruled or to live by the letters, whether of the old or the new testaments. Or else he or she will be living another person's style of life and experience.
Because the Holy Spirit who inspired the writing of the scriptures is greater than any known letters of the bible, hence the need for the New Creation to be led by the Holy Spirit of truth of God always.
The letters of both the old testament and the new testament only reveals how God peculiarly spoke to and led the people of those days, times and seasons individually and collectively; And this is for us to learn from and know how to hear God lead us in life by the Holy Spirit who must relate with us on personal basis.

Sons of God in Christ Jesus are always led by the Holy Spirit.