89 In every age of the Church's history, the mind of man, enlightened by faith, has aimed at the greatest possible knowledge of things divine. It is fitting, then, that the Christian people should also desire to know in what sense they are said in the canon of the Mass to offer up the sacrifice. To satisfy such a pious desire, then, We shall here explain the matter briefly and concisely.
Source: Mediator Dei (Vatican.va)