Baptismus est principium spiritualis vitae, et ianua sacramentorum. Eucharistia vero est quasi consummatio spiritualis vitae, et omnium sacramentorum finis.
"Baptism is the source of spiritual life, and the gate of the sacraments. Eucharist in truth is as it were the consummation of spiritual life and the point of all the sacraments."
Summa Theologiae pars 3 q. 73 art. 3