In this week’s parshah the Torah gives us the mitzvah of tefillah – davening to Hashem – for as the pasuk says, “oso sa’avod – you shall serve Him.” The Torah repeats this mitzvah several times, with another mention further in this week’s parshah: “uleavdo bechal levavchem – serve Him with all of your heart.” The Sifri explains that one serves with his heart by means of tefillah.