In Exodus 30:17-21, God commanded Moses to make a bronze basin and put it between the tent of meeting and the altar. Moses was to put water in the basin for Aaron, the priest, and his children to wash their hands and feet before going up to the altar to offer sacrifices. When the Jewish Temple was destroyed, and there was no longer altar of sacrifice, the washing ritual was moved to the dining table to preserve the tradition of washing. That was how it became the Jewish tradition to wash hands before eating.