A Chassid of Reb Leib Sara's wished to carry his masters trunk for him, but found it too heavy to lift. The Rabbi picked it up and carried it without difficulty. He explained, “in Psalm 103:20 we read, “You, mighty in strength, who fulfill His word.” Both physical and spiritual strength is essential for those who desire to fulfill God's word (Gevurot Ari, page 15).
We are asking God in this blessing for both the physical and spiritual strengths that are necessary to fulfill His word. We focus on the great strength necessary to properly fulfill all the laws of Pesach.