2 Kings 22:8

The book of the law] As the book found in the Temple was brief enough to be read at a single assembly (2 Kings 23:2), whereas the reading of the Law by Ezra occupied several days (Nehemiah 8:18), it can scarcely have included the whole of the Pentateuch; and the religious reforms that Josiah carried out after its discovery and perusal (2 Kings 23:4.) point to its being Deuteronomy only. Deuteronomy contains a record of Moses' farewell address to his countrymen, and reproduces much of the Mosaic legislation that is comprised in Exodus 20-23, 34. But it does not profess to be written by Moses (indeed, in its present form it cannot proceed from him since it gives an account of his death, Exodus 34:5), and there are certain features in it which, when compared with other parts of the Pentateuch and with the history of the period between Moses and Joshua, have led many scholars to conclude that it was composed after the time of Moses out of materials of earlier date. Its concealment in the Temple was probably due to the persecution of the worshippers of the Lord by Manasseh, for it condemns in particular those idolatries which Manasseh practised.