The letters in the New Testament are divine instructions, instructing us to be who we are in Christ Jesus.
The NT letters are saying to us “you have been made righteous; therefore, act as righteous people. This is how righteous people act. This is how Kingdom people live”.
The NT letters are expressions and precepts of righteousness – righteousness as expressed through the lives of each NT writer, inspired by the Spirit of God.
There is only one commandment, because all righteousness is summed up in it. This commandment is summed up in the nature of the new creation in Christ Jesus. It is the nature of God’s own divine life – a life that cannot be confined or limited to rules and laws, but finds its expression in a righteous life