Shemittah and bitachon

 Rav Chaim Shmuelevitz (Sichos Mussar 5731 Bitachon): Concerning the mitzva of Shemitta (leaving land fallow on the seventh year)… It is a very demanding and difficult mitzva. However, it is not just for the sake of spiritual elevation alone - since we see that the sin of neglecting the mitzva is the cause for the Jewish people being exiled from Israel… This is indicative of the greatness of Israel. All are required to being like the angels and if they don’t succeed they are punished severely with exile. But why? Of the different reasons offered for this mitzva - the most important one is that it serves to implant in the heart of every Jew the attribute of bitachon - trusting G‑d. Once in seven years, it is required that all Jews live one whole year in a highly transcendent manner - without any clear material and natural basis. They are required to rely entirely on G‑d to provide for them and to trust Him. This year of Shemitta implants within each Jew bitachon in G‑d. The spiritual flame thus created burns until the next Shemitta year. This attribute is absolutely required for the People of G‑d. That is why its consequences are so severe.