Parashas Eikev · Passuk 8:14
beware lestclest Heb. pen; moved down from v. 12 for clarity. your heart grow haughty and you forget the ETERNAL your God—who freed you from the land of Egypt, the house of bondage;
Torah Temimah points to Sotah 5a.
TT lemma: ורם לבבך ושכחת (unit 3 of 3).
English: Whence the warning against the arrogant? R’ Nachman bar Yitzchak said: from “and your heart grows haughty and you forget Hashem,” and from “Guard yourself lest you forget Hashem” (11:16), and according to R’ Ila’a that every “hishamer” is a negative commandment. Since haughtiness can lead to forgetting, there is a prohibition against being arrogant.
Custom (lo ta’aseh against arrogance)
There is a scriptural warning against ga’avat ruach, built from the link between haughtiness and forgetting God.