“All the liturgy service of Yahweh was prepared that day. They kept the Passover and offered burnt offerings on the altar of Yahweh, according to the command of King Josiah. The people of Israel who were present kept the Passover at that time, as well as the festival of unleavened bread seven days long. No Passover like it had been kept in Israel since the days of the prophet Samuel. None of the kings of Israel had kept such a Passover as was kept by King Josiah,. The priests and the Levites, and all Judah and Israel, and the inhabitants of Jerusalem were present. In the eighteenth year of the reign of King Josiah this Passover was kept.”
This biblical author goes back to 2 Kings, chapter 23 to finish up this celebration. They also kept the feast of the Unleavened Bread for 7 days. This was the greatest Passover ever. They said the same things about the Passover of King Hezekiah, in chapter 30 of this book. Notice that it says those present and not all Judah and Israel. It is interesting that this biblical author mentions Israel since it no longer existed in the north. The inhabitants of Jerusalem seem to be listed separately quite often. This all took place when Josiah was 25 years old.