Deuteronomy 17:18
And it shall be, when he sitteth upon the throne of his kingdom, that he shall write him a copy of this law in a book out of that which is before the priests the Levites:
And it shall be, when he sitteth upon the throne of his kingdom,.... When he is settled on it, and is even amidst all the pomp and glory of it: that he shall write him a copy of this law in a book; which copy the Septuagint and Vulgate Latin versions interpret of this book of Deuteronomy, which is a summary abstract and repetition of the various laws of God to the people of Israel; though the Jewish writers commonly understand it of the whole Pentateuch, the five books of Moses; which perhaps may be enlarging it too much, as it would be reducing it to too little to restrain it to this law concerning kings, as the Targum of Jonathan. The word "Mishneh", rendered "copy", signifies "double"; hence some take it to mean a double exemplar or copy of the law he was obliged to write out, whereby it would be the more imprinted on his mind, and he would be furnished with it for his use at home and abroad, as the Jewish writers observe; so Jarchi by the copy understands two books of the law, one to be left in his treasury, the other to go out and in with him. The same is said in the Talmud {m}, and with which Maimonides {n} agrees, whose words are,
"at the time a king sits on the throne of his kingdom, he writes for himself a book of the law, besides what his fathers left him; and he copies it out of the book of the court by the order of the sanhedrim of seventy one; if his fathers have left him none, or it is lost, he writes two books of the law, one he leaves in the house of his treasures, which he is commanded, as everyone of Israel is, and the second never departs from him;''
but one may seem sufficient on all occasions, and for all purposes; and this was to be wrote out of that which is before the priests and Levites; the original copy of it, which was deposited in the side of the ark; see Deuteronomy 31:26.
{m} T. Bab. Sanhedrn, fol. 21. 2.
{n} Ut supra (Maimon. Hilchot Sanhedrin, c. 2.), sect. 1.