Deuteronomy 17:18

It is in striking consistency with the dignity which everywhere throughout the Mosaic legislation surrounds the chosen people of God, that even if they will be “like as all the nations about” Deuteronomy 17:14, and be governed by a king, care should nevertheless be taken that he shall be no Oriental despot. He is to be of no royal caste, but “one from among thy brethren” Deuteronomy 17:15; he is to bear himself as a kind of “primus inter pares,” his heart “not being lifted up above his brethren” Deuteronomy 17:20; he is, like his subjects, to be bound by the fundamental laws and institutions of the nation, and obliged, as they were, to do his duty in his station of life with constant reference thereto. The spirit of the text is that of Matthew 23:9.

A copy of this law - The whole Pentateuch, or, at any rate, the legal portion of the Pentateuch.

A book ... before the priests the Levites - Compare the marginal reference.