Parashas Eikev · Passuk 8:10
When you have eaten your fill, give thanks to the ETERNAL your God for the good land given to you.
Torah Temimah points to Yerushalmi Berachos 1:1.
TT lemma: ואכלת ושבעת וברכת (unit 5 of 14).
Sefaria — Yerushalmi Berachos 1:1
English: R’ Zeira in the name of R’ Yirmeyah says: If one is in doubt whether he recited the blessing over his food, he must bless, as it is written, “you shall eat and be satisfied and bless.”
Custom (safek on Birkat HaMazon)
A doubt whether one said Birkat HaMazon requires repeating it, as a safek de’oraita.