1 Corinthians 5:6

6.Your glorying is not good. He condemns their glorying, not simply because they extolled themselves beyond what is lawful for man, but because they delighted themselves in their faults. He had previously stripped mankind of all glory; for he had shown that, as they have nothing of their own, whatever excellence they may have, they owe the entire praise of it to God alone. (1 Corinthians 4:7.) What he treats of here, however, is not that, God is defrauded of his right, when mortals arrogate to themselves the praise of their excellences, but that the Corinthians are guilty of arrant folly in extolling themselves without any just ground. For they proudly gloried as if everything had been in a golden style among them, while in the meantime there was so much among them that was wicked and disgraceful.

Know ye not That they might not think that it was a matter of little or no importance that they gave encouragement to so great an evil, he shows the destructive tendency of indulgence and dissimulation in such a case. He makes use of a proverbial saying, by which he intimates that a whole multitude is infected by the contagion of a single individual. For this proverb has in this passage (286) the same meaning as in those expressions of Juvenal: “A whole herd of swine falls down in the fields through disease in one of their number, and one discolored grape infects another.” (287) I have said in this passage, because Paul, as we shall see, makes use of it elsewhere (Galatians 5:9) in another sense.

grex totus in agris
Unius scabie cadit, et porrigine porci:
Uvaque conspecta livorem ducit ab uva
Juv. II. 79-81.