Deuteronomy 17

14. When thou . . . shalt say, I will set a king over me--In the following passage Moses prophetically announces a revolution which should occur at a later period in the national history of Israel. No sanction or recommendation was indicated; on the contrary, when the popular clamor had effected that constitutional change on the theocracy by the appointment of a king, the divine disapproval was expressed in the most unequivocal terms ( 1 Samuel 8:7 ). Permission at length was granted, God reserving to Himself the nomination of the family and the person who should be elevated to the regal dignity ( 1 Samuel 9:15 , 10:24 , 16:12 , 1 Chronicles 28:4 ). In short, Moses foreseeing that his ignorant and fickle countrymen, insensible to their advantages as a peculiar people, would soon wish to change their constitution and be like other nations, provides to a certain extent for such an emergency and lays down the principles on which a king in Israel must act. He was to possess certain indispensable requisites. He was to be an Israelite, of the same race and religion, to preserve the purity of the established worship, as well as be a type of Christ, a spiritual king, one of their brethren.

15. thou mayest not set a stranger over thee, which is not thy brother--that is, by their free and voluntary choice. But God, in the retributions of His providence, did allow foreign princes to usurp the dominion ( Jeremiah 38:17 , Matthew 22:17 ).

16. he shall not multiply horses to himself--The use of these animals was not absolutely prohibited, nor is there any reason to conclude that they might not be employed as part of the state equipage. But the multiplication of horses would inevitably lead to many evils, to increased intercourse with foreign nations, especially with Egypt, to the importation of an animal to which the character of the country was not suited, to the establishment of an Oriental military despotism, to proud and pompous parade in peace, to a dependence upon Egypt in time of war, and a consequent withdrawal of trust and confidence in God. ( 2 Samuel 8:4 , 1 Kings 10:26 , 2 Chronicles 1:16 , 9:28 , Isaiah 31:3 ).

17. Neither shall he multiply wives to himself, that his heart turn not away--There were the strongest reasons for recording an express prohibition on this point, founded on the practice of neighboring countries in which polygamy prevailed, and whose kings had numerous harems; besides, the monarch of Israel was to be absolutely independent of the people and had nothing but the divine law to restrain his passions. The mischievous effects resulting from the breach of this condition were exemplified in the history of Solomon and other princes, who, by trampling on the restrictive law, corrupted themselves as well as the nation.
neither shall he greatly multiply . . . silver and gold--that is, the kings were forbidden to accumulate money for private purposes.

18-20. he shall write him a copy of this law in a book--The original scroll of the ancient Scriptures was deposited in the sanctuary under the strict custody of the priests Each monarch, on his accession, was to be furnished with a true and faithful copy, which he was to keep constantly beside him, and daily peruse it, that his character and sentiments being cast into its sanctifying mould, he might discharge his royal functions in the spirit of faith and piety, of humility and a love or righteousness.

20. that he may prolong his days in his kingdom, he and his children--From this it appears that the crown in Israel was to be hereditary, unless forfeited by personal crime.