52 The Jews therefore strove among themselves, saying: How can this man give us his flesh to eat? 53 Then Jesus said to them: Amen, amen I say unto you: Except you eat the flesh of the Son of man, and drink his blood, you shall not have life in you. 54 He that eateth my flesh, and drinketh my blood, hath everlasting life: and I will raise him up in the last day.
Theophylact: It is not the flesh of man simply, but of God: and it makes man divine, by inebriating him, as it were, with divinity.
Augustine: There are some who promise men deliverance from eternal punishment, if they are washed in Baptism and partake of Christ’s Body, whatever lives they live. The Apostle however contradicts them, where he says, The works of the flesh are manifest, which are these; adultery, fornication, uncleanness, lasciviousness, idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, envyings, murders, drunkeness, revelings, and such like; of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God [Gal 5:19-21]. . . . Heretics and schismatics, who are cut off from the unity of the body, may receive the same Sacrament; but it does not profit them, nay, rather is hurtful, as tending to make their judgment heavier, or their forgiveness later. Nor ought they to feel secure in their abandoned and damnable ways, who, by the iniquity of their lives, desert righteousness, i.e. Christ; either by fornication, or other sins of the like kind. Such are not to be said to eat the body of Christ; forasmuch as they are not to be counted among the members of Christ For, not to mention other things, men cannot be members of Christ, and at the same time members of an harlot.
By this meat and drink then, He would have us understand the society of His body, and His members, which is the Church, in the predestined, and called, and justified, and glorified saints and believers. The Sacrament whereof, i.e. Of the unity of the body and blood of Christ, is administered, in some places daily, in others on such and such days from the Lord’s Table: and from the Lord’s Table it is received by some to their salvation, by others to their condemnation. But the thing itself of which this is the Sacrament, is for our salvation to every one who partakes of it, for condemnation to none.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. IV (London: Rivington, 1845).