Hebrews 9:7

the high priest only enter'd, and that but once every year, when he carried the blood, which he offered for himself, and for the errors of the people.

Hebrews 9:25

nor to make a frequent offering of himself, as the high priest every year enters into the holy of holies with other blood than his own.

Hebrews 10:3

whereas their annual sacrifices were accompanied with an anniversary commemoration of their sins.

Hebrews 10:14

for by one single oblation he has purified for ever those that are sanctified.

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
the high priest only enter'd, and that but once every year, when he carried the blood, which he offered for himself, and for the errors of the people.
Hebrews 10:3
whereas their annual sacrifices were accompanied with an anniversary commemoration of their sins.