And I will make an everlasting covenant with them… – Jeremiah 32:40

In the previous chapter, in the thirty-first verse, this covenant is called “a new covenant”; and it is new in contrast with the former one which the Lord made with Israel when He brought them out of Egypt. It is new as to the principle upon which it is based. The Lord had said unto His people, that if they would keep His laws and walk in His statutes, He would bless them. He set before them a long line of blessings, rich and full: all these would be their portion if they would hearken to the Lord and obey His law…But under the exceedingly favourable circumstances in which they lived in the wilderness, where they had no temporal cares, and no neighbours to mislead them, they did not keep the statutes of their God; nay, they did not even remain faithful to Him as their God; for they worshipped a molten image and likened the Lord of Glory to an ox that eateth grass…Thus they brake the covenant in the most wanton and wicked manner. Such a covenant was easily violated by a rebellious people; therefore the Lord, in His immeasurable grace, resolves to make with them a covenant of a new kind, which cannot thus be broken…In these days the Lord hath, in Christ Jesus, made with the true seed of Abraham, even with all believers, a new covenant; not after the tenor of the old, nor liable to be broken as it was. Brethren, take care to distinguish between the old and the new covenants; for they must never be mingled. Many never catch the true idea of the covenant of grace; they do not understand a compact of pure promise. They talk about grace, but they regard it as dependent upon merit. They speak about God’s mercy, and then combine with it conditions which make it rather justice than grace. Distinguish between things which differ. If salvation be of grace, it is not of works, otherwise grace is no more grace; and if it be of works, it is not of grace, otherwise work is no more work. The new covenant is all of grace, from its first letter to its closing word. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2108.cfm