Israel is represented by the Old Man and Judah by the younger
O house of Israel, cannot I do with you as this potter? saith the LORD. Behold, as the clay is in the potter's hand, so are ye in mine hand, O house of Israel. 7 At what instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy it; 8 If that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them. 9 And at what instant I shall speak concerning a nation, and concerning a kingdom, to build and to plant it; 10 If it do evil in my sight, that it obey not my voice, then I will repent of the good, wherewith I said I would benefit them. 11 Now therefore go to, speak to the men of Judah, and to the inhabitants of Jerusalem, saying, Thus saith the LORD; Behold, I frame evil against you, and devise a device against you: return ye now every one from his evil way, and make your ways and your doings good.
Jeremiah 3:6-10 The LORD said also unto me in the days of Josiah the king, Hast thou seen that which backsliding Israel hath done? she is gone up upon every high mountain and under every green tree, and there hath played the harlot. (7) And I said after she had done all these things, Turn thou unto me. But she returned not. And her treacherous sister Judah saw it. (8) And I saw, when for all the causes whereby backsliding Israel committed adultery I had put her away, and given her a bill of divorce; yet her treacherous sister Judah feared not, but went and played the harlot also. (9) And it came to pass through the lightness of her whoredom, that she defiled the land, and committed adultery with stones and with stocks. (10) And yet for all this her treacherous sister Judah hath not turned unto me with her whole heart, but feignedly, saith the LORD.
I believe that God has shown me when He compares Jerusalem and Judah in the Old Testament, spiritually "Judah" is the "New Testament Church". It is then you can begin to see eternal salvation is not given to those who perpetually insist on living lives of disobedience and rebellion. But, if the Jewish teachers can get Christians and everyone else to believe that Israel is given to all who claim to be Jew by blood (Matthew 3:8-9) regardless of heart and lifestyle, then the eternal security of Christians under the New Covenant must be true as well, except they are both false.
Jeremiah 9:24-26 But let him that glorieth glory in this, that he understands and knows and knows me , that I am the LORD which exercise lovingkindness, judgment, and righteousness, in the earth: for in these things I delight, saith the LORD. 25 Behold, the days come, saith the LORD, that I will punish ALL them which are circumcised WITH the uncircumcised; 26 Egypt, and Judah, and Edom, and the children of Ammon, and Moab, and all that are in the utmost corners, that dwell in the wilderness: for ALL these nations [this includes Judah] are uncircumcised, and ALL [national not individual] the house of Israel are uncircumcised in the heart.
1Corinthians 3:23 And ye are Christ's; and Christ is God's.