In the law of Moses, indeed in the Bible as a whole, there is much stress laid on outward behavior and how we are to treat our neighbors. Yet the Mosaic law is clear that mere external conformity to its demands is insufficient. The Lord demands an obedience that goes far deeper than that. His standards must be on our heart—they must impact our motives, thinking, emotions, and everything else that we are both inside and out (Deut. 6:6). This is a hard truth to grasp, which is why God emphasizes it from the beginning of His dealings with the people of Israel. The five books of Moses often stress the need for a circumcised heart that is set apart to love the Lord above all else (10:12, 16). Jeremiah emphasizes the need for a changed heart in today’s passage by reminding his readers of our hearts’ condition apart from God’s grace. Born in sin, our hearts are “deceitful above all things, and desperately sick” (Jer. 17:9). We do not, apart from Christ, love the truth. We rationalize the irrational and defend the indefensible. We harbor malice, lust, covetousness, and all manner of secret sins. This is what Scripture tells us from beginning to end (Rom. 1:18–32). Matthew Henry comments, “There is wickedness in our hearts which we ourselves are not aware of and do not suspect to be there.” The prophet Jeremiah saw this so clearly because of the era in which he lived. During Josiah’s reign, Judah enjoyed what appeared to be a great revival, culminating in one of the grandest Passover celebrations ever (2 Chron. 34:1–35:19). However, though Josiah had true piety, the nation as a whole experienced only a skin-deep revival. Jeremiah 17:1–4 reveals that the people never truly gave up “their altars and their Asherim, beside every green tree and on the high hills.” The hearts of the people under Josiah were far from God, and there was only rote observation of true religion. Ultimately, the people were not trusting God and His Word, but they looked to whoever was currently in charge to direct their piety. There was no deep personal attachment to the Lord, so the people were just as happy worshipping the gods of Canaan as they were praising Yahweh. Josiah was a good man, much better than his grandfather Manasseh (2 Kings 21:1–18; 22:1–23:30). Nevertheless, because the Judahites trusted in the king, not in the Lord, reformation did not go far enough. It is always folly to trust mere men for one’s reconciliation to God, no matter how good and holy such men happen to be (Jer. 17:5–8).