If any man be in Christ, he/she is a New Creature: the new creature is the product of the New Covenant God established in Jesus Christ. The New Creature is designed to live in, by and under the New Covenant in Christ Jesus; it therefore becomes imperative that the New Creature (Born Again person) learns the truth of the New Covenant (Testament) and respond to it by faith. Here is the term of the New Covenant in Christ Jesus: Hebrews 8:10-13
[10]For this is the covenant that I will make with the house of Israel after those days, says the Lord: I will imprint My laws upon their minds, even upon their innermost thoughts and understanding, and engrave them upon their hearts; and I will be their God, and they shall be My people.
[11]And it will nevermore be necessary for each one to teach his neighbor and his fellow citizen or each one his brother, saying, Know (perceive, have knowledge of, and get acquainted by experience with) the Lord, for all will know Me, from the smallest to the greatest of them.
[12]For I will be merciful and gracious toward their sins and I will remember their deeds of unrighteousness no more. [Jer. 31:31-34.]
[13]When God speaks of a new [covenant or agreement], He makes the first one obsolete (out of use). And what is obsolete (out of use and annulled because of age) is ripe for disappearance and to be dispensed with altogether. (AMPLIFIED BIBLE)