Sforno on Leviticus 25:19/ספורנו על ויקרא כ״ה:י״ט

1ואכלתם לשובע, the produce of the land will prove nutritious. An example of this is the manna when the same quantity, an omer per head, whether for a baby or a fully grown person proved adequate, showing that G’d had imbued it with the nutrients needed by the person eating it. [It was the most individualised diet ever. Ed.] Our sages describe this as an example of food adjusting to the body’s needs after it had come into a person’s entrails. (Torat Kohanim, Bechukotai 1,7) This is also how we can understand that the crops grown in the sixth year of the sh’mittah cycle were able to be sufficient for the people’s needs during the seventh year.

2וישבתם לבטח עליה, you will not need to be embarrassed by having to import food because your land did not provide you with sufficient means of nutrition.