Ignatius of Antioch
"I have no taste for corruptible food nor for the pleasures of this life. I desire the bread of God, which is the flesh of Jesus Christ, who was of the seed of David; and for drink I desire his blood, which is love incorruptible" (Letter to the Romans 7:3 [A.D. 110]).
"Take note of those who hold heterodox opinions on the grace of Jesus Christ which has come to us, and see how contrary their opinions are to the mind of God. . . . They abstain from the Eucharist and from prayer because they do not confess that the Eucharist is the flesh of our Savior Jesus Christ, flesh which suffered for our sins and which that Father, in his goodness, raised up again. They who deny the gift of God are perishing in their disputes" (Letter to the Smyrnaeans 6:2–7:1 [A.D. 110]).
Justin Martyr
"We call this food Eucharist, and no one else is permitted to partake of it, except one who believes our teaching to be true and who has been washed in the washing which is for the remission of sins and for regeneration [i.e., has received baptism] and is thereby living as Christ enjoined. For not as common bread nor common drink do we receive these; but since Jesus Christ our Savior was made incarnate by the word of God and had both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Eucharistic prayer set down by him, and by the change of which our blood and flesh is nurtured, is both the flesh and the blood of that incarnated Jesus" (First Apology 66 [A.D. 151]).
Irenaeus
"If the Lord were from other than the Father, how could he rightly take bread, which is of the same creation as our own, and confess it to be his body and affirm that the mixture in the cup is his blood?" (Against Heresies 4:33–32 [A.D. 189]).
"He has declared the cup, a part of creation, to be his own blood, from which he causes our blood to flow; and the bread, a part of creation, he has established as his own body, from which he gives increase unto our bodies. When, therefore, the mixed cup [wine and water] and the baked bread receives the Word of God and becomes the Eucharist, the body of Christ, and from these the substance of our flesh is increased and supported, how can they say that the flesh is not capable of receiving the gift of God, which is eternal life—flesh which is nourished by the body and blood of the Lord, and is in fact a member of him?" (ibid., 5:2).
This is just a start. The good Lord, who desires each of us with a fervent love, humbled Himself to be born in poverty, in a manger, of a woman. This same God the Son died on the Cross so that we might live. Now, IMO, this goes to the passage in the Bible that says (paraphrase) that God's ways are not our ways. Not only are they, "not our ways", but they are quite incomprehensible to us. Nothing He does to show His love is done in a way men think makes sense. Not the least of which...is there a man among us would establish his kingdom by dying? I don't think so, man considers that weakness, not strength.
So the Eucharist is consistent with who the Almighty God has already shown us He is. He humbles Himself and becomes "bread", probably the most basic of the foods, recognized everywhere as nourishment, and He nutures our everlasting soul as regular bread nourishes our mortal flesh.
This teaching of the Catholic Church has been since the beginning, and always will be.
As the Bible says, "This teaching is hard, who can accept it?" John 6:60
