Mishnayos Brachos Perek 8 Mishnah 4

בית שמאי אומרים: מכבדין את הבית – A place where they ate [a meal], we put the room in order (i.e. clean it/sweep it} from the remnants of the food that became crumbled on it, and afterwards, we wash our hands with מים אחרונים/The Latter Waters, since there are times when the attendant is an עם ארץ/ignoramus (and someone not necessarily punctilious in the separation of tithe) and he leaves the crumbs of an olive’s bulk there, and if one says that one should wash one’s hands first, you might lose the foods from the “Latter Waters/מים אחרונים” that spray on them and become detestable. The School of Hillel holds that it is prohibited to use an attendant who is an ignoramus (of Jewish law, especially, the laws of ritual purity), since an attendant who is a Torah scholar would not leave crumbs of an olive’s bulk, but would remove them, and if the water ( מים האחרונים) sprays upon the crumbs, it is meaningless, since those crumbs do not add up to an olive’s bulk, it is permitted to get rid of them with one’s hand. But the Halakha is in accordance with the School of Shammai in that it is permissible to use an attendant who is an ignoramus.