"It was suitable for him to be in us divinely by the Holy Spirit. It was also suitable for him to be mingled with our bodies by his holy flesh and precious blood, which we possess as a life-giving Eucharist, in the form of bread and wine. God feared that seeing actual flesh and blood placed on the holy tables of our churches would terrify us. Humbling himself to our infirmities, God infuses into the things set before us the power of life. He transforms them into the effectiveness of his flesh, that we may have them for a life-giving participation, that the body of life thus might be found in us as a life-producing seed. Do not doubt that this is true. Christ plainly says, 'This is my body. This is my blood.' In faith, receive the Savior's word. Since he is the truth, he cannot lie. You will honor him. The wise John says, 'He that receives his witness has set his seal that God is true. For he whom God sent speaks the words of God.' The words of God, of course, are true. In no way whatsoever can they be false. Although we cannot understand how God does that, yet he himself knows the way of his works."
-St. Cyril of Alexandria in his Commentary on Luke, Homily 142.