מדרש על חגיגה 11:26

R. Yossi Haglili says: Three mitzvoth obtain on a festival: the festive offering (chagigah), the sacrifice of peace-offerings, viz. (27:7) "And you shall sacrifice peace-offerings and you shall eat them there"; "appearance" (re'iah), before the L-rd with a burnt-offering, viz. Shemoth 23:15); and rejoicing (simchah).