I recently began another read through Jeremiah. So here are a few random thoughts that struck me. In 9:23-26 there is a pivotal text also referenced by Paul (1 Cor. 1:31). In 9:24 we read that Yahweh “practices lovingkindness, justice, and righteousness.”
עֹ֥שֶׂה חֶ֛סֶד מִשְׁפָּ֥ט וּצְדָקָ֖ה
Many years ago in seminary I examined the relationship between justice (מִשְׁפָּ֥ט) and righteousness (וּצְדָקָ֖ה) relative to their occurrences in Isaiah. At the time, it seemed that in particular “justice” carries a dual focus depending on what is happening. I had begun translating the word as a phrase “appropriate justice”; that is, when God acts, for the one in faith, appropriate justice is salvation, but for the one outside faith, appropriate justice is condemnation and judgment.
So in this context of Jeremiah 9, God invites “those who boast in the Lord” to share in that which delights Yahweh (9:23-24). On the other hand, the one who does not boast, the “uncircumcised” (nations or Israel, uncircumcised in heart) will experience “appropriate justice” in the judgment, “in the days which are coming.”
That also seems to fit with Paul’s eschatological understanding in 1 Corinthians, and in particular 1:30-31. “But by His doing you are in Christ Jesus, who became to us wisdom from God, and righteousness and sanctification, and redemption, so that, just as it is written, ‘Let him who boasts, boast in the Lord.’ ” (NAS 95)