Carefulness With Brachos is Evidence of a Pure Heart

Rabenu Bechaya (Kad Hakemach, Erech Bracha) writes that since the Torah tells us to recite Birchas Hamazon, one has an important obligation to do so and one who does this is displaying that he has strong emunah and a pure heart, and that he is also a chasid and one who fears Hashem.