And it came to pass, when the king had heard the words of the book of the law, that he rent his clothes.

Wesley's Notes

22:11 The words - The dreadful comminations against them for the sins still reigning among the people. If Josiah had seen and read it before, which seems more probable, yet the great reverence which he justly bare to the original book, and the strange, and remarkable, and seasonable finding of it, had awakened and quickened him to a more serious and diligent consideration of all the passages contained in it. And what a providence was this, that it was still preserved! Yea, what a providence, that the whole book of God is preserved to us. If the holy scriptures had not been of God, they had not been in being at this day. God's care of the bible, is a plain proof of his interest in it. It was a great instance of God's favour, that the book of the law was thus seasonably brought to light, to direct and quicken that blessed reformation, which Joash had begun. And it is observable, they were about a good work, repairing the temple, when it was found. They that do their duty according to their knowledge, shall have their knowledge increased.

Matthew Henry's Concise Commentary

22:11-20 The book of the law is read before the king. Those best honour their Bibles, who study them; daily feed on that bread, and walk by that light. Convictions of sin and wrath should put us upon this inquiry, What shall we do to be saved? Also, what we may expect, and must provide for. Those who are truly apprehensive of the weight of God's wrath, cannot but be very anxious how they may be saved. Huldah let Josiah know what judgments God had in store for Judah and Jerusalem. The generality of the people were hardened, and their hearts unhumbled, but Josiah's heart was tender. This is tenderness of heart, and thus he humbled himself before the Lord. Those who most fear God's wrath, are least likely to feel it. Though Josiah was mortally wounded in battle, yet he died in peace with God, and went to glory. Whatever such persons suffer or witness, they are gathered to the grave in peace, and shall enter into the rest which remaineth for the people of God.