The Mass is derogatory to Christ's one sacrifice (James Buchanan)

[Reformed Covenanter]

Either Christ's one sacrifice has procured the remission of sins, or it has not. If it has procured remission, then no other sacrifice is either necessary, on the one hand, or admissible on the other … The repetition of sacrifice by the Popish Church is derogatory to that one sacrifice, and virtually amounts to a declaration that the Cross of Christ must be supplemented by the Mass.

James Buchanan, On the “Tracts for the Times.” (Edinburgh: John Johnstone, 1843), pp 67-68.