We are his members and we are nourished by creation, which is his gift to us, for it is he who causes the sun to rise and the rain to fall. He declared that the chalice which comes from his creation was his blood, and he makes it the nourishment of our blood. He affirmed that the bread which comes from his creation was his body, and he makes it the nourishment of our body.
When the chalice we mix and the bread we bake receive the word of God, the eucharistic elements become the body and blood of Christ, by which our bodies live and grow. How then can it be said that flesh belonging to the Lord's own body and nourished by his body and blood is incapable of receiving God's gift of eternal life? Saint Paul says in his Letter to the Ephesians that we are members of his body, of his flesh and bones. He is not speaking of some spiritual and incorporal kind of person, for spirits do not have flesh and bones. He is speaking of a real human body composed of flesh, sinews, and bones, nourished by the chalice of Christ's blood and receiving growth from the bread which is his body.
Irenaeus of Lyons (AD 140-200), Adversus Haereses 5, 2, 2-3: SC 153, 30-38