"And when you will say, 'What will we eat in the seventh year? For we have neither sown nor gathered our harvest.' And I will command my blessing to you, in the sixth year. And it will make the harvest enough for three years." (Vayikra, 25:20,21)
The verse seems to be saying that "because" the Jews would ask, "What will we eat?" - therefore, I will command My blessing. It seems to imply that if the Jews would have stronger faith (and not ask "What will we eat?") - then there would not be a blessing on the sixth year's harvest! How is this to be understood?
G-d sustains the world by means of 1) 'natural' phenomena, and 2) open miracles.
We might think that when the world experiences open miracles, a greater degree of appreciation for G-d is appropriate than when things are running 'naturally'. Actually, the opposite is true. A 'natural' phenomenon, consistently recurring since Creation, is G-d's greatest demonstration of His intervention - more deserving of appreciation than a one-time display.
When Am Yisroel is spiritually elevated, this is how we perceive 'nature'. And it is to such a perspective that this verse refers. With fulfillment of the command to let the Land lie fallow, the Jews understand that G-d will sustain them through miracles. And they say (The word say is used, rather than 'ask', showing that the question is rhetorical), "What will we eat in the seventh year? For we have neither sown nor gathered our harvest." They don't doubt that there will be food. They have no fear that G-d will forget His People. What disturbs them is that their food will not come from 'natural' phenomena, "For we have neither sown nor gathered our harvest" - their sustenance will come from that lower level of G-dly intervention: open miracles. They would have preferred it to come from His daily and constant intervention: 'natural' phenomena - which is a higher level.
To this, G-d answers, "And I will command My blessing to you, in the sixth year. And it will make the harvest enough for three years." Even when we fulfill the mitzvah of letting the Land lie fallow, G-d promises that His intervention will not be from open miracles, but through an exceedingly abundant harvest. G-d's intervention will continue to manifest itself in 'natural' phenomena. (Sfas Emes, B'har 5637)
Rav Meir Simcha haKohan, zt"l, (Meshech Chochma Parshs B'chukosai) uses this concept to explain a seeming contradiction in the Talmud: In Tractate B'rochos (4b), it says that anyone who recites Psalm 145 of T'hillim, three times daily, is assured a place in The World to Come. (Therefore, we recite this psalm, beginning with "Ashrei" - every day - twice during Shacharis, and once again during Mincha). Yet in Tractate Shabbos (118b), it states that anyone who recites Hallel every day is guilty of blasphemy! Since both Psalm 145 and Hallel are praises of G-d, why is it beneficial to recite the former, constantly - while daily recitation of the later is blasphemous?
Hallel praises G-d for miracles of a one-time nature: the Exodus; the splitting of the Sea, and of the Jordan River, etc. To recite these praises daily, would imply that open miracles are more important and more praiseworthy than those miracles which G-d disguises in 'natural' phenomena. This is blasphemy.
Psalm 145, however, praises G-d for the miracles of 'natural' phenomena - for the way He keeps the world running 'naturally'. One who has internalized this perspective of G-d and 'nature', to the extent that he proclaims it three times daily, has a place in The World to Come.
