1 Cor. 5:8. But with the unleavened bread of purity and truth.
That is, leading a life that is blameless or pure, as opposed to a corrupt life, and true, that is, sincere, without any deceit, as opposed to craftiness. Or: in the word "truth" you can understand an opposition to the Old Testament types, which were not the truth; for it is required that a Christian be above the Old Testament types. Or again: by "purity" you can understand purity in practice, and by "truth" correctness in contemplation.
1 Cor. 5:9. I wrote to you in my epistle not to associate with fornicators.
In which epistle? In this very same one. For when he said above, "purge out the old leaven," hinting at the fornicator, as was shown, then from these words it was already evident that one must not mingle with fornicators. But since they might think that one must withdraw from all fornicators, even from those who were among the Greeks, he explains which fornicators he is speaking of.
1 Cor. 5:10. Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then you would need to go out of the world.
He used the word "at all" to express the common knowledge of the matter. And the meaning is this: however, I do not forbid associating at all with the fornicators of the world, that is, with the pagans, otherwise you would have had to seek another universe. Indeed, when so many pagans live in the same city as you, how is it possible not to associate with them?
1 Cor. 5:11. But I wrote to you not to associate with anyone who, while calling himself a brother, remains a fornicator, or a covetous person, or an idolater, or a reviler, or a drunkard, or a rapacious person; with such a one not even to eat together.
You see, it was not only one fornicator, but others as well, and not just one vice, but various ones. But in what way can a brother also be an idolater? Just as the Samaritans were once only half-pious, so it happened with the Corinthians as well, that is, some of them still clung to idols. Beyond this, the apostle prepares to speak about those who ate food sacrificed to idols. He well said, "who is called a brother"; for anyone who is guilty of the sins enumerated above bears only the name of brother, but in reality is not a brother. The word ή πόρνος can be taken in the sense of a disjunctive conjunction (ή), as in the expressions that follow it, but it can also be taken as the verb "to remain" (ή), so that if anyone, being called a brother, remains (υπάρχη) a fornicator, and so on. "With such a person do not even eat together," so that he may recognize himself as defiled on account of sin and refrain from it.
1 Cor. 5:12. For what have I to do with judging outsiders?
He calls the Greeks "those without" and the Christians "those within." I, he says, have no concern at all for those without; they live outside my laws; consequently, it is superfluous to prescribe divine commandments to those who live outside the fold of Christ. "Whatever the law says, it says to those who are under the law" (Rom. 3:19).
1 Cor. 5:12-13. Do you not (ουχί) judge those who are inside? But those who are outside God judges.
Some, after the particle ουχί ("not, no"), place a period; then they read the following words without a question, thus: you judge those who are inside. That is, the apostle, having said above, "what have I to do with judging outsiders," now added ουχί — no, that is, it is not my business to judge them. But others read it conjunctively and with a question: "Do you not judge those who are inside?" — that is, is it not Christians whom you ought to judge? As for outsiders, the Dreadful Judgment of God awaits them, from which those inside will be delivered, if they receive judgment from you.
1 Cor. 5:13. Therefore cast out the wicked one from among you.
He brought to mind an Old Testament saying (see Deut. 13:5), wishing to show that already before it was pleasing to the lawgiver that impious people be cut off from the community. With the words "from among you" he shows that it will be more beneficial for them if they cast out the impious one from themselves.