The ceremonies to be observed on the day of atonement have been already described in Leviticus 16:1-34, where it found its place as the great purification of the people and of the sanctuary. Here it is reintroduced as one of the holy days.
It is the one Jewish fast; to be observed as a day of holy convocation, a day in which to afflict your souls and to offer an offering made by fire unto the Lord, and in which no manner of work was to be done; inasmuch as, like the weekly sabbath, it was a sabbath of rest from the ninth day of the month at even, from even unto even.
The time of year at which it was appointed shows that one purpose of its institution was to make solemn preparation for the joyous festival of Tabernacles, which was to follow in five days' time, when the people ought to be in a state of reconciliation with God.