What is the origin of Yom Kippur and when was it first observed?
Yom Kippur began after Moses came down from Mount Sinai for the second time after breaking the original tablet of the Ten Commandments. The Israelites were worshiping a golden calf which caused a separation between them and God. To make up for this, they fasted, prayed, and repented. Ever since, the tradition has remained to hold it at the end of the holy ays of Rosh Hashana.