And Hilkiah the high priest said unto Shaphan the scribe, I have found the book of the law in the house of the LORD. And Hilkiah gave the book to Shaphan, and he read it. I have found the book of the law - Was this the autograph of Moses? It is very probable that it was, for in the parallel place; 2 Chronicles 34:14, it is said to be the book of the law of the Lord by Moses. It is supposed to be that part of Deuteronomy (28, 29, 30, and 31), which contains the renewing of the covenant in the plains of Moab, and which contains the most terrible invectives against the corrupters of God's word and worship.
The rabbins say that Ahaz, Manasseh, and Amon endeavored to destroy all the copies of the law, and this only was saved by having been buried under a paving-stone. It is scarcely reasonable to suppose that this was the only copy of the law that was found in Judea; for even if we grant that Ahaz, Manasseh, and Amon had endeavored to destroy all the books of the law, yet they could not have succeeded so as to destroy the whole. Besides, Manasseh endeavored after his conversion to restore every part of the Divine worship, and in this he could have done nothing without the Pentateuch; and the succeeding reign of Amon was too short to give him opportunity to undo every thing that his penitent father had reformed. Add to all these considerations, that in the time of Jehoshaphat teaching from the law was universal in the land, for he set on foot an itinerant ministry, in order to instruct the people fully: for "he sent to his princes to teach in the cities of Judah; and with them he sent Levites and priests; and they went about through all the cities of Judah, and taught the people, having the book of the Lord with them;" see 2 Chronicles 17:7-9. And if there be any thing wanting to show the improbability of the thing, it must be this, that the transactions mentioned here took place in the eighteenth year of the reign of Josiah, who had, from the time he came to the throne, employed himself in the restoration of the pure worship of God; and it is not likely that during these eighteen years he was without a copy of the Pentateuch. The simple fact seems to be this, that this was the original of the covenant renewed by Moses with the people in the plains of Moab, and which he ordered to be laid up beside the ark; (Deuteronomy 31:26); and now being unexpectedly found, its antiquity, the occasion of its being made, the present circumstances of the people, the imperfect state in which the reformation was as yet, after all that had been done, would all concur to produce the effect here mentioned on the mind of the pious Josiah.