"..The principal excellence of the most Holy Sacrifice of the Mass consists in being essentially, and in the very highest degree, identical with that which was offered on the Cross of Calvary: with this sole difference that the sacrifice on the Cross was bloody, and made once for all, and did on that one occasion satisfy fully for all the sins of the world; while the sacrifice of the altar is an unbloody sacrifice, which can be repeated an infinite number of times, and was instituted in order to apply in detail that universal ransom which Jesus paid for us on Calvary..."
St. Leonard of Port Maurice.