2 Kings 22:8

And Hilkiah the high priest said unto Shaphan the scribe,....

Some think this book was the autograph, or original manuscript, of the five books of Moses, under his own hand; others think it was only an ancient and authentic copy. Most likely it was that which, by the command of Moses, was laid up in the most holy place, Deut. xxxi.

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; 2Ch 34:14, it is said to be the book of the law of the Lord by Moses.

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].

Some have concluded from this discovery, either that no “book of the law” had ever existed before, the work now said to have been “found” having been forged for the occasion by Hilkiah; or that all knowledge of the old “book” had been lost, and that a work of unknown date and authorship having been at this time found was accepted as the Law of Moses on account of its contents, and has thus come down to us under his name. But this is to see in the narrative far more than it naturally implies. If Hilkiah had been bold enough and wicked enough to forge, or if he had been foolish enough to accept hastily as the real “book of the law” a composition of which he really knew nothing, there were four means of detecting his error or his fraud: (1) The Jewish Liturgies, which embodied large portions of the Law; (2) The memory of living men, which in many instances may have extended to the entire five books, as it does now with the modern Samaritans; (3) Other copies, entire or fragmentary, existing among the more learned Jews, or in the Schools of the prophets; and (4) Quotations from the Law in other works, especially in the Psalmists and prophets, who refer to it on almost every page. The copy of the Book of the Law found by Hilkiah was no doubt that deposited, in accordance with the command of God, by Moses, by the side of the ark of the covenant, and kept ordinarily in the holy of holies (marginal reference). It had been lost, or secreted, during the desecration of the temple by Manasseh, but had not been removed out of the temple building.