John Gill Commentary Deuteronomy 6:2

"that thou mightest fear Jehovah thy God, to keep all his statutes and his commandments, which I command thee, thou, and thy son, and thy son`s son, all the days of thy life; and that thy days may be prolonged." — Deuteronomy 6:2 (ASV)

That you might fear the Lord your God
Being taught to know the greatness of his being, and the nature of his mind and will, and the manner of his worship; and not with a slavish fear, but with a filial one, a reverential affection for God; being instructed in their duty, as of children, to their God and Father; see (Deuteronomy 5:29)

to keep all his statutes, and his commandments, which I command you ;
not in his own name, but in the name, and by the authority of God, whose minister and messenger he was; and all, having the stamp of divine authority on them, were to be observed and kept, and not one to be neglected or departed from:

you, and your son, and your son's son, all the days of your life ;
a man and his children, and grandchildren; he was to take care that they kept all the commandments of the Lord as long as he lived, and had any concern with them:

and that your days may be prolonged ;
long life being reckoned a very great outward mercy; a long enjoyment of, and continuance in the land of Canaan, is chiefly designed, which is usually expressed when this is observed; see (Deuteronomy 4:26Deuteronomy 4:40) (Deuteronomy 5:16Deuteronomy 5:33) .