Devarim 17:20

20 That his lev be not lifted up in pride above his brethren, and that he turn not aside from the mitzvah, to the right hand, or to the left; to the end that he may prolong his days in his mamlachah, he, and his banim, in the midst of Yisroel.

Devarim 17:20 Meaning and Commentary

Deuteronomy 17:20

That his heart be not lifted up above his brethren
On account of his office, the dignity of it, considering that he was subject to the law of God, and accountable to the Lord for all his actions:

and that he turn not aside from the commandment, to the right hand or
to the left;
not in the least deviate from the law of God in the whole of his conduct, and particularly in the exercise of his kingly office:

to the end that he may prolong his days in his kingdom;
ruling well according to the laws of God being the way to rule long:

he and his children in the midst of Israel;
this shows, as Jarchi observes, that if his son was fit for the kingdom, he was to be preferred to any other man; for though it was elective, yet to be continued in the same family, provided they walked in the ways of the Lord, and observed his laws.

Devarim 17:20 In-Context

18 And it shall be, when he sitteth upon the kisei mamlakhto (throne of his kingdom), that he shall write him a mishneh hatorah hazot (copy of this torah) in a sefer out of that which is before the kohanim, the Levi’im;

19 And it shall be with him, and he shall read therein all the days of his life; that he may learn to fear Hashem Elohav, to be shomer over kol divrei hatorah hazot and these chukkim, to do them;

20 That his lev be not lifted up in pride above his brethren, and that he turn not aside from the mitzvah, to the right hand, or to the left; to the end that he may prolong his days in his mamlachah, he, and his banim, in the midst of Yisroel.