And Aaron shall make an atonement upon the horns of it once in a year with the blood of the sin offering of atonements: once in the year shall he make atonement upon it throughout your generations: it is most holy unto the LORD. An atonement - once in a year - On the tenth day of the seventh month. See Leviticus 16:18 (note), etc., and the notes there. See Clarke on Leviticus 16:21 (note), etc.
Related Commentaries of Exodus 30:10
Exodus 30:10
10 And Aaron shall make an atonement upon the horns of it once in a year with the blood of the sin offering of atonements: once in the year shall he make atonement upon it throughout your generations: it is most holy unto the LORD.