Hebrews 9:7

But into the second, the High Priest goes only on one day of the year, and goes alone, taking with him blood, which he offers on his own behalf and on account of the sins which the people have ignorantly committed.

Hebrews 9:25

Nor did He enter for the purpose of many times offering Himself in sacrifice, just as the High Priest enters the Holy place, year after year, taking with him blood not his own.

Hebrews 10:3

But in those sacrifices sins are recalled to memory year after year.

Hebrews 10:14

For by a single offering He has for ever completed the blessing for those whom He is setting free from sin.

Treasury of Scripture Knowledge

Summary

And this shall be an everlasting statute unto you, to make an atonement for the children of Israel for all their sins once a year. And he did as the LORD commanded Moses.

Bible References

Once a year

Hebrews 9:7
But into the second, the High Priest goes only on one day of the year, and goes alone, taking with him blood, which he offers on his own behalf and on account of the sins which the people have ignorantly committed.
Hebrews 10:3
But in those sacrifices sins are recalled to memory year after year.