Hebrews 10:2

Otherwise, they would surely have ceased to be offered; for the worshippers, once cleansed, would no longer be conscious of sins!

Hebrews 9:13-14

For if the blood of goats and bulls and the ashes of a heifer, sprinkled on defiled persons, give them a holiness that bears on bodily purity,

Hebrews 10:17

And their sins and breaches of the law I will remember no more.

Treasury of Scripture Knowledge

Summary

For then would they not have ceased to be offered? because that the worshippers once purged should have had no more conscience of sins.

General references

Bible References

Once

Hebrews 10:17
And their sins and breaches of the law I will remember no more.
Hebrews 9:13
For if the blood of goats and bulls and the ashes of a heifer, sprinkled on defiled persons, give them a holiness that bears on bodily purity,

General references

Hebrews 10:18
Now where these are remitted, an offering for sin exists no longer.