Musar zu Dewarim 32:18

ועתה יגדל נא כח אדנ"י . Both the Pesikta and the Yalkut mention on the verse צור ילדך תשי, "you neglected, or "weakened" the Rock that begot you" (Deut. 32,18), that as long as Israel perform G–d's will, they add to His Power and strength, since Moses has said here: "Now let the Power of G–d become great," (14,17). On the other hand, any time they act contrary to G–d's will, anger Him, they are diminishing His Power, as is evident from that verse in Deuteronomy. This teaches us the tremendous impact human actions have.