The OT anticipated a change of covenant and conduct in the NT ...

Deut.18:17 Then the LORD said to me, “They have spoken well. 18 I will raise up for them a prophet like you from among their brothers. I will put My words in his mouth, and he will tell them everything I command him. 19 And I will hold accountable anyone who does not listen to My words that that prophet speaks in My name. 20 But if any prophet dares to speak a message in My name that I have not commanded him to speak, or to speak in the name of other gods, that prophet must be put to death.”

Jer.31:31 Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah: 32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD: 33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. 34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.

A prophet and a new covenant are both identified as coming and as the full and final revelation of God's will for mankind. The first covenant was always considered a temporary one. The first covenant was primarily a national one with Israel to preserve and protect them as a nation until the advent of the Messiah. The first was a covenant/law of works that served to distinguish the Jewish race and set them apart from the pagan world and to identify their faith with the one true God. The 2nd covenant was intended for the whole world as a covenant of grace to bring salvation to all people by the advent of Jesus Christ. Today we have two witnesses on earth to the truth of the Scriptures--the Jews and the Church--one for each covenant.

A simple illustration is:
We primarily teach young children by rules of do and do not because they cannot understand everything. As they get older we move from the law of dos and do nots to teaching them responsibilities and life principles. When they are young we discipline their errors to guide them and as they age we instruct, but give them grace to learn on their own. We explain the benefits and consequences of choices but we do not force them to do the right thing. We give them unconditional love and grace and are open to a future relationship of mentoring. When they go astray and come back we forgive them and encourage them to do right. This a basic illustrative primer of God's dealings with man--beginning with law and moving to grace and relationship.

Hebrews 10:9 Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second.

Last edited by Thunderstick; 07/02/19.