Hebrews 9:7

but into the inner tent the high priest only goes alone, once a year, and that not without blood, which he offers for himself and for the ignorances of the people.

Hebrews 9:25

Nor did he enter to offer himself repeatedly, as the high priest entered into the sanctuary, year after year, with blood that was not his own;

Hebrews 10:3

But on the other hand, in these sacrifices sins are called to memory, year after year.

Hebrews 10:14

For by one single offering he has perfected forever those whom he is sanctifying.

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 inner tent the high priest only goes alone, once a year, and that not without blood, which he offers for himself and for the ignorances of the people.
Hebrews 10:3
But on the other hand, in these sacrifices sins are called to memory, year after year.