An excerpt from an article by Keith Throop:
God promised through the prophet Jeremiah that He would one day establish a New Covenant with His people, a promise which found its fulfillment in Jesus Christ:
NKJ Jeremiah 31:31-32 “Behold, the days are coming, says the LORD, when 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 lead them out of the land of Egypt, My covenant which they broke, though I was a husband to them, says the LORD.”
Here the Lord says that the New Covenant will be different than the Old Covenant which the the people of Israel broke, and He implies that the difference will be that it will be an unbreakable covenant. That this is so – and how it is so – becomes clear in the following verses:
NKJ Jeremiah 31:33 “But this is the covenant that I will make with the house of Israel after those days, says the LORD: I will put My law in their minds, and write it on their hearts; and I will be their God, and they shall be My people.”
The New Covenant will not be like the old, breakable covenant because God will ensure that those who participate in the New Covenant have the law within their hearts. Indeed, there will be no one who has partaken of the New Covenant who does not have a new heart. Ezekiel put it this way:
NKJ Ezekiel 36:26-27 “I will give you a new heart and put a new spirit within you; I will take the heart of stone out of your flesh and give you a heart of flesh. 27 I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them.”
So we can have assurance that we will be preserved in covenant faithfulness such that we will never lose the blessings of the New Covenant, and this will come about through the gift of the Holy Spirit and the transformation of our hearts. But there is more:
NKJ Jeremiah 31:34 “No more shall every man teach his neighbor, and every man his brother, saying, ‘Know the LORD,’ for they all shall know Me, from the least of them to the greatest of them, says the LORD. For I will forgive their iniquity, and their sin I will remember no more.”
There are two New Covenant blessings mentioned here:
First, unlike the Old Covenant, everyone who is a member of the New Covenant community knows the Lord.
Second, unlike the Old Covenant, everyone who is a member of the New Covenant has his sins forgiven.
It is clear that when God says that all in the New Covenant will know Him, He does not just mean that they will know about Him, but rather that they will have a personal relationship with Him as believers who have been forgiven by Him.