Between the dispersion of Israel (in 722BC) and deportation of Judah (in 586BC), YHVH raised up the prophets Jeremiah and Ezekiel through whom He explained in full to both houses the reasons for their predicament (in spite of the fact that the northern kingdom had already been sacked by then). At the same time, these prophets also laid-out, and elaborated on, Israel's future restoration and redemption.
In speaking to the elders of Israel, now beyond the Great River, Ezekiel reminded them of their history of disobedience and rebellion, but also how their Elohim had responded to their insurrection each and every time. YHVH had "acted for [His] name's sake, that it should not be profaned in the sight of the nations among whom [Israel] lived, in whose sight [He] had made [Himself] known to [Israel]" (Ezekiel 20: 9). Before the Israelites came into the land of Canaan YHVH declared that He was not taking them there for their sake, nor because of their righteousness, but for His namesake, as they were a rebellious and stiff-necked people (ref. Deuteronomy 9: 5-7). However, He was still intending for them to be His witnesses to the nations, just as king David pointed out, that [YHVH] saved [us] for His name sake, so that His might and power would be known, along with His mercy and truth, for why should the nations say: "where is [Israel's] Elohim?" (ref. Psalms 106:8; 115:1).
Now, even though both houses of Israel were cast off, YHVH was continuing to watch over them, for He has not given up His covenants and promises to their ancestors. What's more, although His people had proven to be unable to uphold the Torah, YHVH obviously was not going to do away with His statutes, laws and ordinances, which govern His kingdom, His relationship with His people, nor their destiny. Because He was bound to His own nature and word, nothing was going to come in the way of His progressive plan, not even Israel's utterly fallen nature.
As we have seen all along, Israel was called and chosen as YHVH's firstborn nation, whose forefathers were of the firstborn linage (see chapter XI). They were His inheritance. YHVH even sealed His relationship with them with a very radical declaration: "Thus says YHVH, Who gives the sun for a light by day, the ordinances of the moon and the stars for a light by night, Who disturbs the sea, and its waves roar (YHVH of hosts is His name): ‘If those ordinances depart from before Me, says YHVH, then the seed of Israel shall also cease from being a nation before Me forever.’ Thus says YHVH: ‘If heaven above can be measured, and the foundations of the earth searched out beneath, I will also cast off all the seed of Israel for all that they have done, says YHVH’" (Jeremiah 31: 35-37). But having said all this, YHVH had to embark on an undertaking that would transform the errant hearts which thus far have been in opposition to His plans and purposes.
Here is where a New Covenant comes into play. This covenant was not going to be like the one made in Sinai, which was contingent upon certain conditions and therefore dependent on Israel's ability to choose YHVH's righteousness, via a law written on tablets of stone. This new declared agreement was founded totally on YHVH's mercy and ability to remove the rebellious nature of sin from human hearts, and to grant forgiveness once and for all. The prophet Jeremiah records the terms of this new arrangement: "Behold, the days are coming, says YHVH, when I will make a new covenant with the house of Israel and with the house of Judah --"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 YHVH. But this is the covenant that I will make with the house of Israel after those days, says YHVH: I will put My Torah in their minds, and write it on their hearts; and I will be their Elohim, and they shall be My people…For I will forgive their iniquity, and their sin I will remember no more" (Jeremiah 31:31-34). What a radical promise! Thus the Torah, its laws and statutes, will no longer present an insurmountable challenge. It is the Torah which is at the very heart of the new covenant, as the recipients' new hearts will be Torah-compatible by nature and disposition.
Yet, most amazingly this New Covenant declaration came at a time when Israel was already in exile and Judah was also facing deportation. The peculiar and deliberate timing of announcing this covenant attested to its veracity, and guaranteed that YHVH Himself would carry it out. He promised through Moses that He would raise-up another prophet like him (ref. Deuteronomy 18:15; 18). As we have seen, Moses was YHVH's servant-deliverer from the slavery in Egypt. But now He needed a deliverer, a savior, to bring them out of their slavery and bondage to sin, and to their naturally evil inclination. He needed to bring in a firstborn, a kinsman redeemer who would qualify for this office. This one would have to be both a prince and priest, after the order of Melchitzedec.