Musar do Kapłańska 25:49

The overriding rule to be learned from all this is that man must strive to cleave to his Maker not only with his spiritual faculties but also with his physical attributes. This is the meaning of the promise: "you will dwell securely on the land." Once we have achieved such a level of closeness to G–d, the Torah then proceeds to speak about spiritual rewards in פרשת בחוקותי by promising to transform the rain into something which we will be able to perceive as a spiritual dimension of G–d's largess, as we have already pointed out.