The Passover celebrated the miraculous deliverance of King Josiah’s ancestors from Egyptian bondage by the power of God. Josiah’s ancestors had received this commandment when God brought them out of Egypt:

This is a day to remember. Each year, from generation to generation, you must celebrate it as a special festival to the LORD. This is a law for all time. (Exodus 12:14)

Yet, it had been three generations since the Passover was kept at all. And it had been many generations since the Passover had been fully kept according to God’s Law.

For no such Passover had been kept since the days of the judges who judged Israel, or during all the days of the kings of Israel or of the kings of Judah. But in the eighteenth year of King Josiah this Passover was kept to the LORD in Jerusalem. (2 Kings 23:22-23)

The Passover had gone the way of the Book of the Law, forgotten and abandoned, replaced with altars for false gods, incense burned to false gods, and idols forged, hewn, and carved of false gods.

Our hearts are not worshipfully neutral. Wandering from God and his Word, we will inevitably wonder at the gods of the culture.

Oh, to grace how great a debtor
Daily I’m constrained to be
Let that goodness like a fetter
Bind my wandering heart to Thee
Prone to wander, Lord, I feel it
Prone to leave the God I love
Here’s my heart, oh, take and seal it
Seal it for Thy courts above

(Come, Thou Fount of Every Blessing; Robert Robinson)