John Chrysostom
He proves this again from the Old Testament. Since the greatness of what was said far exceeded their understanding, he persuades them by former and customary examples. He rightly says, "according to the flesh," because they are Israel according to the Spirit. The meaning of his words is this: learn at least from grosser examples that those who eat from sacrifices become participants in the sacrificial offering. Do you see how he proves that those considered perfect do not have perfect knowledge? They do not even know that from such communion a certain friendship with demons arises in many, when little by little they acquire a habit for it. If among men sharing salt and table becomes an occasion and sign of friendship, the same can be true in relation to demons.
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Notice how, concerning the Jews, he did not say that they were sharers of God, but "participants of the altar," because what was offered was burned. But concerning the Body of Christ he does not speak so. How then? It is communion of the Lord’s Body, because we become sharers not of the altar, but of Christ Himself. Having said, "participants of the altar," he feared lest someone think that he was speaking of idols as having some power and being able to cause harm. See how he next rejects this thought and says, "What am I saying then? That an idol is anything, or that what is offered to idols is anything?" (1 Cor 10:19). I say this, he continues, and turn you away from idols, not because they can cause any harm or have any power. They are nothing. But I want you to despise them. If he wants us to despise them, you will say, why does he turn us away from them with such intensity? Because their sacrifices are not offered to your Master.