"Of paramount importance to the writer [of Hebrews] is the effectiveness of the sacrificial death of Christ. He several times emphasizes that it was ‘once for all’ (7:27; 9:12, 26; 10:10). There was never any question of a repetition. It was totally inconceivable that such an offering could ever be inadequate, nor would the re-offering of such a sacrifice be intelligible (cf. 9:26). The writer is convinced that the uniqueness of Christianity rests in the central act of Christ in giving himself as an offering on the cross for the sins of his people."

–– Donald Guthrie, in "Hebrews: An Introduction and Commentary"