I read it every year, but it never fails to impress me.
Here is an excerpt from the second lesson of the Office of Readings for the Saturday of Easter Week, taken from the Catecheses of St. Cyril of Jerusalem (4th century), speaking about the Real Presence of Christ in the Holy Eucharist. From the fourth century !
Once, when speaking to the Jews, Christ said: Unless you eat my flesh and drink my blood you shall have no life in you. This horrified them and they left him. Not understanding his words in a spiritual way, they thought the Savior wished them to practice cannibalism.
Under the old covenant there was showbread, but it came to an end with the old dispensation to which it belonged. Under the new covenant there is bread from heaven and the cup of salvation. These sanctify both soul and body, the bread being adapted to the sanctification of the body, the Word, to the sanctification of the soul.
Do not, then, regard the eucharistic elements as ordinary bread and wine: they are in fact the body and blood of the Lord, as he himself has declared. Whatever your senses may tell you, be strong in faith.
You have been taught and you are firmly convinced that what looks and tastes like bread and wine is not bread and wine but the body and the blood of Christ. You know also how David referred to this long ago when he sang: Bread gives strength to man’s heart and makes his face shine with the oil of gladness. Strengthen your heart, then, by receiving this bread as spiritual bread, and bring joy to the face of your soul.
May purity of conscience remove the veil from the face of your soul so that by contemplating the glory of the Lord, as in a mirror, you may be transformed from glory to glory in Christ Jesus our Lord. To him be glory for ever and ever. Amen.