“Holy Place.” This holy place behind the inner veil of the Temple is often called “the Holy of Holies,” (cp. Exod. 26:33).
“appear in the cloud.” The bright glory that surrounds God was often described as a cloud. See commentary on Ezekiel 1:28.
[Leviticus 16 is about the Day of Atonement. For more information and a more complete list of the feasts and sabbaths in Israel, see commentary on Lev. 23:2.]