Deuteronomy 17:20

20 that his heart may not be lifted up above his brethren, and that he may not turn aside from the commandment, either to the right hand or to the left; so that he may continue long in his kingdom, he and his children, in Israel.

Deuteronomy 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.

Deuteronomy 17:20 In-Context

18 "And when he sits on the throne of his kingdom, he shall write for himself in a book a copy of this law, from that which is in the charge of the Levitical priests;

19 and it shall be with him, and he shall read in it all the days of his life, that he may learn to fear the LORD his God, by keeping all the words of this law and these statutes, and doing them;

20 that his heart may not be lifted up above his brethren, and that he may not turn aside from the commandment, either to the right hand or to the left; so that he may continue long in his kingdom, he and his children, in Israel.