תּוספֿתּא אויף דברים 12:5

One who is impure is exempt from appearing [before the Temple on the three festivals], as it says (Deut. 12:5-6), "you are to come there and you are to bring there [your burnt-offerings and your sacrifices]." Since one must be [ritually] fit to enter the Temple Courtyard, consequently one who is impure, who is not fit to enter the Temple Courtyard[, is exempt from appearing].