John Gill Commentary Deuteronomy 8:17

"and [lest] thou say in thy heart, My power and the might of my hand hath gotten me this wealth." — Deuteronomy 8:17 (ASV)

And you say in your heart
These words are in connection with the former part of the (Deuteronomy 8:14) :

and you forget the Lord your God ;
the author and giver of all the good things enjoyed, and think within themselves, though they might not express it in words at length:

my power and the might of mine hand has gotten me this wealth ;
so ascribing that to themselves, their labour, and diligence, which ought to be ascribed to the bounty and blessing of God; see (Hosea 12:8) .