Today the Church celebrates the memorial of Saint Leo the Great, who became pope in 440 and was made a Doctor of the Church in 1754.
Pope John XXIII marked the Fifteenth Centennial of Saint Leo the Great's death in 1961 with the encyclical Aeterna Dei Sapientia (God's Eternal Wisdom) quoting a sermon by Saint Leo:
"The reception of Christ's Body and Blood does nothing less than transform us into that which we consume, and henceforth we bear in soul and body Him in whose fellowship we died, were buried, and are risen again" (Serm. 64. 7 on the Passion, PL 54. 357).
Saint Leo the Great, pray for us!