Per History, tradition holds that Yom Kippur began after Moses recieved the Ten Commandments atop Mount Sinai. After making his way down he saw his people worshipping a golden calf — a false idol — and destroyed the tablets. When Israel repented of its idolatry, God forgave their sin and replaced the stones of the Ten Commandments that Moses shattered in his wrath. This was said to be on the 10th day of the month of Tishrei, the first in the Jewish calendar, and so became the day of atonement.
Yom Kippur became marked by special services over the years. It was the only time that the high priest of Jerusalem entered the holy of holies, the inner sanctum of the temple and home to the Ark of the Covenant. There, the priest would forego his usual resplendent golden robes, instead wearing simple white after a ritualized bath, per Chabad.org. He would burn incense, use a lottery to choose a sacrifice between two goats (the “loser” was set free), and sprinkle the blood of the sacrifice upon the ark.
This ritual was intended to beseech God on all Israel’s behalf for forgiveness, and Yom Kippur made Jerusalem a site of pilgrimage for Jews throughout the region. Following the destruction of the Second Temple in 70 A.D., a modified version of the high priest’s service was adopted by local rabbis, and individual worshippers were encouraged to call for God’s mercy within themselves.
