When Christ gave the Bread He did not say “This is the symbol of My Body” but “This is My Body”. In the same way when He gave the cup He did not say “This is the symbol of My Blood” but “This is My Blood”; for He wanted us to look upon the Eucharistic elements after their reception of grace and the coming of the Holy Spirit not according to their nature, but that we receive them as they are: the Body and Blood of our Lord.
–Theodore of Mopsuestia (c. 350-428)