The New Internal Covenant was promised in the Book of Jeremiah 31as a “law written on our hearts” and was fulfilled by Jesus at the cross. Of all the quotes of the Old Testament in the New Testament, Hebrews 8:8-13 is the longest and it is a quote from Jeremiah 31. Here what it says:
“If the first covenant had been faultless, there would have been no need for a second covenant to replace it. But when God found fault with the people, he said:
“The day is coming, says the LORD,
when I will make a new covenant
with the people of Israel and Judah.
This covenant will not be like the one
I made with their ancestors
when I took them by the hand
and led them out of the land of Egypt.
They did not remain faithful to my covenant,
so I turned my back on them, says the LORD.
But this is the new covenant I will make
with the people of Israel on that day, says the LORD:
I will put my laws in their minds,
and I will write them on their hearts.
I will be their God,
and they will be my people.
And they will not need to teach their neighbors,
nor will they need to teach their relatives,
saying, ‘You should know the LORD.’
For everyone, from the least to the greatest,
will know me already.
And I will forgive their wickedness,
and I will never again remember their sins.”
When God speaks of a “new” covenant, it means he has made the first one obsolete. It is now out of date and will soon disappear.”
It has been done as it was said it would be done.
“Jesus took some bread and blessed it. Then he broke it in pieces and gave it to the disciples, saying, “Take it, for this is my body.”
And he took a cup of wine and gave thanks to God for it. He gave it to them, and they all drank from it. And he said to them, “This is my blood, which confirms the covenant between God and his people. It is poured out as a sacrifice for many.” Jesus