[Then] they bring [it] before him; he eats dipped lettuce before he reaches the course that is secondary to the matzah. [Now] they brought before him matzah, lettuce, and charoses, and two cooked dishes; although charoses is not a mitzvah.  R' Eliezer bar R' Tzadok says: [The dipping is] a mitzvah.  And in the Temple they would bring before him the body of the pesach-[offering].