Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Deu 17:1-7) All sacrifices to be perfect, Idolaters must be slain.
(Deu 17:8-13) Difficult controversies.
(Deu 17:14-20) The choice of a king, His duties.
No creature which had any blemish was to be offered in sacrifice to God. We are thus called to remember the perfect, pure, and spotless sacrifice of Christ, and reminded to serve God with the best of our abilities, time, and possession, or our pretended obedience will be hateful to him. So great a punishment as death, so remarkable a death as stoning, must be inflicted on the Jewish idolater. Let all who in our day set up idols in their hearts, remember how God punished this crime in Israel.
Courts of judgment were to be set up in every city. Though their judgment had not the Divine authority of an oracle, it was the judgment of wise, prudent, experienced men, and had the advantage of a Divine promise.
God himself was in a particular manner Israel's King; and if they set another over them, it was necessary that he should choose the person. Accordingly, when the people desired a king, they applied to Samuel, a prophet of the Lord. In all cases, God's choice, if we can but know it, should direct, determine, and overrule ours. Laws are given for the prince that should be elected. He must carefully avoid every thing that would turn him from God and religion. Riches, honours, and pleasures, are three great hinderances of godliness, (the lusts of the flesh, the lusts of the eye, and the pride of life,) especially to those in high stations; against these the king is here warned. The king must carefully study the law of God, and make that his rule; and having a copy of the Scriptures of his own writing, must read therein all the days of his life. It is not enough to have Bibles, but we must use them, use them daily, as long as we live. Christ's scholars never learn above their Bibles, but will have constant occasion for them, till they come to that world where knowledge and love will be made perfect. The king's writing and reading were as nothing, if he did not practise what he wrote and read. And those who fear God and keep his commandments, will fare the better for it even in this world.