St. Thomas Aquinas
“The Church’s sacraments are ordained for helping man in the spiritual life. But the spiritual life is analogous to the corporeal, since corporeal things bear a resemblance to spiritual. Now it is clear that just as generation is required for corporeal life, since thereby man receives life; and growth, whereby man is brought to maturity: so likewise food is required for the preservation of life. Consequently, just as for the spiritual life there had to be Baptism, which is spiritual generation; and Confirmation, which is spiritual growth: so there needed to be the sacrament of the Eucharist, which is spiritual food.”
Source: St. Thomas Aquinas, Summa Theologica