Leviticus 16 - G. Campbell Morgan's Exposition on the Whole Bible

The great Day of Atonement was perhaps the most important of the whole year in the Hebrew economy. On that day provision was made for dealing with the whole question of sin as known and unknown. When considering the sin and trespass offerings, we saw that in each case, in greater or less degree, the element of accountability was conditioned in knowledge. Sin, however, in the sight of God is still sin, even though committed in ignorance. All such must be dealt with.

Careful instructions were given for the observance of the day. It was the one day in the year on which the high priest entered into the Holy of Holies. Every arrangement was intended to impress the mind with the solemnity of approach to God and to emphasize the fact that man as a sinner has no right of access save as he approaches through sacrifice. It is significant that when the priest entered the Holiest of all he did not wear his gorgeous apparel, but was clothed in a garment of simple and pure white linen. Careful instructions, moreover, were given as to the attitude of the people on that day. They were to rest and afflict their souls, which means that the day must be observed as one of solemn fasting and humiliation in which they would remind themselves of the fact of their sin or the provision made for their cleansing and of the consequent right of approach to God in worship.