Sefer Ezri Me’im Hashem relates the following in the name of Rav Moshe Soloveitchik zt”l: A person is obligated to fully believe that tefillos are always heard and have the power to bring about yeshuos.
Rav Moshe was once speaking to a sick person whom the doctors had given up hope for. He told him: “The pasuk says (Tehillim 121:2): ‘My help is from Hashem creator of Heaven and earth.’ Why doesn’t it just say that our help is from Hashem? Why does it add that He is the creator of Heaven and earth? The answer is that we are saying that Hashem created this world from nothing, which teaches us that even if there is no natural way to help someone, Hashem can create something from nothing to save that person. That is what we must have in mind when we daven.”
With this in mind, he explained the greatness of Yehoshua’s act of stopping the sun in its place. It would seem that the greatness of this act was that he had the power to stop the sun in its tracks. In truth, however, the greatness of Yehoshua is seen from the fact that he davened to Hashem and asked Him to change nature. Most people would never even think to daven for such a thing. But Yehoshua possessed such strong emunah that he asked Hashem for this miracle to occur as if he were asking for anything else. A prayer uttered with such intense emunah will always be heard and can alter the course of nature.
