The Greek verb (tetelestai) is in the perfect tense, indicating an achievement with lasting results. It might be rendered, "It has been and remains forever accomplished." For Christ has made what the Letter to the Hebrews calls "one single sacrifice for sins" (Heb. 10:12 NJB) and what Cranmer in the Book of Common Prayer called "a full, perfect and sufficient sacrifice, oblation and satisfaction for the sins of the whole world." In consequence, because Christ has finished the work of sin bearing, there is nothing left for us to do, or even to contribute.
-John Stott in Through the Bible Through the Year, p. 261