“Then you shall remember Hashem, your G-d; that it was He Who gave you strength to be successful.” (8:18)
R’ Yosef Chaim of Baghdad z”l, the ‘Ben Ish Chai’, writes: This verse teaches us a fundamental concept, i.e. that all that a person receives from this world comes to him from Hashem Himself. It does not come to man through his own strength or handiwork.
However, man’s nature is to attribute his success to his own hard work. Therefore, Hashem has given us three mitzvot that remind us that we are not in control of our own physical well-being. Fulfilling these mitzvot helps us recognize that Hashem is the One Who gives us the tools to succeed in life, that everything is His, and thatwe are always receiving from Him.
One of these is the mitzvah of Shemittah, letting the land lie fallow every seventh year. One who fulfills this mitzvah acknowledges that the Land is not his and that everything belongs to Hashem. Another such mitzvah is Berachot, reciting blessings before eating. By doing so, one acknowledges that everything belongs to Hashem. A third such mitzvah is the prohibition on Ribit/interest and the commandment to give free loans to one’s brethren. One who observes this acknowledges that all the money that he has belongs to Him as well.
The initials of these 3 mitzvot spell “BASAR”/”flesh.” This reminds us that (in the words of Tehilim 136:25), “He gives nourishment to all flesh.” and we are fully dependant on Hashem.