Jeremiah 9

v23-24. This is what the Lord says: "Let not the wise man boast of his wisdom or the strong man boast of his strength or the rich man boast of his riches, but let him who boasts boast about this: that he understands and knows me, that I am the Lord, who exercises kindness, justice and righteousness on earth, for in these I delight," declares the Lord.

we have no right to boast about anything that we have or can do. like how i said yesterday, Boethius was miserable because he thought he lost his good fortune. but his justification technically didn't work because nothing was his in the first place, everything was given to him by God. in the same way, God gets angry and displeased when we become prideful of our blessings because God can take them away in a second. who are we to think that we obtained all those things by our own power? it's only by God's grace that we are given these things. and when we boast in how great God is, then He becomes pleased.

v25. "The days are coming" declares the Lord, "when I will punish all who are circumcised only in the flesh [...] for all these nations are really uncircumcised, and even the whole house of Israel is uncircumcised in heart."

what these people were doing was acting all holy and righteous (circumcised only in the flesh), but God knew how dirty they were. like white-washed tombs...they were rotten and evil and sinful all on the inside. for them to act holy like that externally while they're stained with sin is like straight up lying to God.