Reference for Deuteronomy 14:25

Food which is in separate pieces does not combine together [to receive impurity], according to Rabbi Dosa ben Harkinas. But the Sages say: “It does combines together.” One may exchange [ produce of] second tithe for uncoined metal, according to Rabbi Dosa. But the Sages say: “One may not so exchange it.” The hands [alone] need to be immersed for the waters of purification according to Rabbi Dosa. But the Sages say: “If his hands have become unclean his whole body becomes unclean.”