The reason for the Sages’ designating specifically the Patriarchs as G-d’s chariot, although every Jew’s body becomes a “chariot” when he performs a mitzvah, is that the Patriarchs’ submission to the Divine will was unique in its power, its scope, and its consistency. All their organs were totally surrendered to the Divine will throughout their lives—whereas with other Jews, only those organs which perform a mitzvah are a “chariot,” and then only during the act. In fact, the same organ which today served as a “chariot” to G-d’s will might conceivably serve the opposite purpose tomorrow.