Q. Why is a “Washing-Cup” needed for the ritual hand-washing?

A. The Temple had a special basin designed for ritual washing (called the KIYOR) and in one of the processes of ritual purification it says “put spring water on it, in a vessel” (Numbers 19:17). There is also a law that requires the flow of water to be a direct effect of human force, which is best and most directly done using a vessel.