Tohoros 7:4-5
Tohoros 7:4
Let’s say that the wife of a learned person left the wife of an unlearned person grinding grain in her house. If the handmill stopped turning, the house is unclean but if the handmill didn’t stop turning, then only the part of house that she can reach out and touch with her hand is unclean. If there were two women, Rabbi Meir says that the house is unclean regardless of whether or not the handmill stopped because one woman could be touching things while the other is grinding. The Sages say that only the part that she can reach out and touch with her hand is unclean.
Tohoros 7:5
Let’s say that a learned person left an unlearned person in his house to guard it. If the owner can see the people who enter and exit the house, then only food, liquids and uncovered earthenware vessels are unclean; couches, chairs and earthenware vessels with tight-fitting lids remain clean. If he can’t see the people entering and/or exiting the house, then everything is unclean. This is so even if the unlearned person needs assistance to get around, and even if he was physically tied up.