And Hilkiah the high priest said unto Shaphan the scribe, I have found the {e} book of the law in the house of the LORD. And Hilkiah gave the book to Shaphan, and he read it.

(e) This was the copy that Moses left them, as it appears in 2Ch 34:14, which either by the negligence of the priests had been lost, or else by the wickedness of idolatrous kings had been abolished.

Wesley's Notes

22:8 The book - That original book of the law of the Lord, given or written by the hand of Moses, as it is expressed, 2Chron 34:14, which by God's command was put beside the ark, Deut 31:26, and probably taken from thence and hid, by the care of some godly priest, when some of the idolatrous kings of Judah persecuted the true religion, and defaced the temple, and (which the Jewish writers affirm) burnt all the copies of God's law which they could find. It was now found among the rubbish, or in some secret place.

Jamieson-Fausset-Brown Bible Commentary

2Ki 22:8-15. Hilkiah Finds the Book of the Law.

8-11. Hilkiah said . I have found the book of the law in the house of the Lord, &c.-that is, the law of Moses, the Pentateuch. It was the temple copy which, had been laid (De 31:25, 26) beside the ark in the most holy place. During the ungodly reigns of Manasseh and Amon-or perhaps under Ahaz, when the temple itself had been profaned by idols, and the ark also (2Ch 35:3) removed from its site; it was somehow lost, and was now found again during the repair of the temple [Keil]. Delivered by Hilkiah the discoverer to Shaphan the scribe [2Ki 22:8], it was by the latter shown and read to the king. It is thought, with great probability, that the passage read to the king, and by which the royal mind was so greatly excited, was a portion of Deuteronomy, the twenty-eighth, twenty-ninth, and thirtieth chapters, in which is recorded a renewal of the national covenant, and an enumeration of the terrible threats and curses denounced against all who violated the law, whether prince or people. The impressions of grief and terror which the reading produced on the mind of Josiah have seemed to many unaccountable. But, as it is certain from the extensive and familiar knowledge displayed by the prophets, that there were numbers of other copies in popular circulation, the king must have known its sacred contents in some degree. But he might have been a stranger to the passage read him, or the reading of it might, in the peculiar circumstances, have found a way to his heart in a manner that he never felt before. His strong faith in the divine word, and his painful consciousness that the woeful and long-continued apostasies of the nation had exposed them to the infliction of the judgments denounced, must have come with overwhelming force on the heart of so pious a prince.

Matthew Henry's Concise Commentary

22:1-10 The different event of Josiah's early succession from that of Manasseh, must be ascribed to the distinguishing grace of God; yet probably the persons that trained him up were instruments in producing this difference. His character was most excellent. Had the people joined in the reformation as heartily as he persevered in it, blessed effects would have followed. But they were wicked, and had become fools in idolatry. We do not obtain full knowledge of the state of Judah from the historical records, unless we refer to the writings of the prophets who lived at the time. In repairing the temple, the book of the law was found, and brought to the king. It seems, this book of the law was lost and missing; carelessly mislaid and neglected, as some throw their Bibles into corners, or maliciously concealed by some of the idolaters. God's care of the Bible plainly shows his interest in it. Whether this was the only copy in being or not, the things contained in it were new, both to the king and to the high priest. No summaries, extracts, or collections out of the Bible, can convey and preserve the knowledge of God and his will, like the Bible itself. It was no marvel that the people were so corrupt, when the book of the law was so scarce; they that corrupted them, no doubt, used arts to get that book out of their hands. The abundance of Bibles we possess aggravates our national sins; for what greater contempt of God can we show, than to refuse to read his word when put into our hands, or, reading it, not to believe and obey it? By the holy law is the knowledge of sin, and by the blessed gospel is the knowledge of salvation. When the former is understood in its strictness and excellence, the sinner begins to inquire, What must I do to be saved? And the ministers of the gospel point out to him Jesus Christ, as the end of the law for righteousness to every one that believeth.