"Consider therefore the Bread and the Wine not as bare elements, for they are, according to the Lord's declaration, the Body and Blood of Christ; for even though sense suggests this to you, yet let faith establish you. Judge not the matter from the taste, but from faith be fully assured without misgiving, that the Body and Blood of Christ have been vouchsafed to you."
- St. Cyril of Jerusalem, Cathechetical Lectures 22:6
"The body which is born of the holy Virgin is in truth body united with divinity, not that the body which was received up into the heavens descends, but that the bread itself and the wine are changed into God's body and blood"
- St. John of Damascus, Exact Exposition of the Orthodox Faith, IV:13
Consubstantiation sounds heretical to me.