St. Ignatius of Antioch (c. 110 A.D.)
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 )
Take care, then, to use one Eucharist, so that whatever you do, you do according to God:
FOR THERE IS ONE FLESH OF OUR LORD JESUS CHRIST , and one cup
IN THE UNION OF HIS BLOOD ; one
ALTAR , as there is one bishop with the presbytery…
( Letter to the Philadelphians 4:1 )
They [i.e. the Gnostics] 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 the Father, in his goodness, raised up again.
( Letter to Smyrnians 7:1 )
St. Justin the Martyr (c. 100 - 165 A.D.)
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 [Baptism], and is thereby living as Christ has 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 nourished,
IS BOTH THE FLESH AND THE BLOOD OF THAT INCARNATED JESUS .
( First Apology , 66)
St. Cyril of Jerusalem (c. 350 A.D.)
For just as the bread and the wine of the Eucharist
before the holy invocation of the adorable Trinity were
simple bread and wine, but the invocation having been made, the bread becomes the Body of Christ and the wine the Blood of Christ … **(
Catechetical Lectures 19 [Mystagogic 1], 7
Once in Cana of Galilee
He changed the water into wine , a thing related to blood; and is
His changing of wine into Blood not credible ? When invited to an ordinary marriage, with a miracle He performed that glorious deed. And is it not much more to be confessed that
He has betowed His Body and His Blood upon the wedding guests ?
( 22 [Mystagogic 4], 2 )
Do not , therefore, regard the Bread and the Wine
as simply that ;
for they are, according to the Master’s declaration, the Body and Blood of Christ. Even though the senses suggest to you the other, let faith make you firm. Do not judge in this matter by taste, but – be fully assured by the faith, not doubting that you have been deemed worthy of the Body and Blood of Christ .
( 22 [Mystagogic 4], 6 )
Much more…
http://www.therealpresence.org/eucharst/father/fathers.htm