Heb 10:10-14
"And by that will we have been sanctified through the offering of the body of Jesus Christ once for all. And every priest stands daily at his service, offering repeatedly the same sacrifices, which can never take away sins. But when Christ had offered for all time a single sacrifice for sins, he sat down at the right hand of God."
The definitive contrast: the priests stand (work never finished), Christ sat down (work accomplished). 'Once for all' (ephapax) — the absolute sufficiency of Christ’s sacrifice. It does not need to be repeated — neither in the mass nor in any other rite.