John 19:30: "when he had taken the vinegar, Jesus said, 'It is finished,' and he bowed his head and gave up his spirit."
The Greek expression translated "It is finished" is a single word: tetelestai. It is completed: it is fulfilled. The word was used by tax collectors, who marked it on a bill, with the meaning: paid in full.
See what Scott Hahn has to say about this in Eucharist, Holy Meal; particularly what he says about "The Fourth Cup". There we read how that Jesus' saying, "It is finished" refers primarily to the completion of the Passover liturgy begun in the Upper Room. Also, how His definitive Sacrifice has made all other bloddy sacrifice ineffectual, and thus worthless from then on.
Interesting. I didn't know that.