Vaetchanan: Chapter 16
Waste water before the door

Rabbi Chiya tells us that people must not spill waste water between the doorposts because a demon lies there and sees everything that is done in the house, and the waste water will give him permission to cause harm. We are told about the role of the Mezuzah, and Rabbi Chiya says that wherever the Holy Name abides people are safe from the accusations of the evil ones.