(Vayikra 17:15) "and every soul that eats neveilah (carcass) or treifah (what is "torn") … he shall wash his clothes and bathe in water …" R. Yitzchak says: It is written (Ibid. 16) "And if he does not wash (his clothes) and he does not bathe his flesh (and he eats kodshim or enters the sanctuary), he shall bear his sin." For not bathing his body Scripture makes him liable to kareth ("cutting-off').
You say, it is for not bathing his body, but perhaps it is for not washing his clothes! — Can you say this? If for the more stringent tumath meth he is not punished (with kareth) for not washing his clothes, how much more so is he not punished for not washing his clothes for the less stringent eating of carcass! If so, what is the intent of "And if he does not wash his clothes"? To serve as an exhortation (against not washing them).