The Great Commentary of Cornelius à Lapide
1 Corinthians 5:8
Therefore let us keep the feast. The Latin has, "Let us banquet," because feasts were wont to be celebrated with solemn banquets in token of rejoicing.
The feast here is either the feast of the Passover or of unleavened bread. And notice that, according to Exod.xii., the evening of the fourteenth day of the month, or of the Passover, was not, strictly speaking, the feast, but the following morning was, which was called the feast of the first day of unleavened bread, and lasted for seven days, during which nothing but unleavened bread was allowed to be eaten; and before those days, viz., in the fourteenth day of the first month Nisan, instead of the Paschal lamb that had been killed, they killed other Paschal victims, viz., burnt offerings and peace-offerings. Cf. Numbers 28:19. The meaning, therefore, is this: Christ, having been sacrificed for us as our Passover, has redeemed us, and has begun for us the feast of unleavened bread. Therefore, after this Passover, after the death and redemption of Christ, let us keep this spiritual feast of unleavened bread, that we may be unleavened and pure, and may consequently feed on unleavened things, i.e., may enjoy purity of life for the seven says of our life. As all our time is measured by seven revolving days, seven is a symbol of completeness, and therefore the seven days mentioned here denote the whole of life here below. Through that life we are to keep up the memorial of Christ's redemption, of our Paschal Lamb, by purity of life that befits Christians, and by sacrifices and praises.
But since the evening of the Passover could also be joined with the following morning, as the Jews reckoned their feasts from evening to evening, hence this evening may also be called a feast, or at all events a festive sacrifice and banquet of a lamb. Hence the Latin version is, "Let us banquet." Hence a second meaning can be gathered, which is this: "Let us keep a perennial Passover: let the Paschal feast be to us a continuous feast throughout the day of life, by our daily feeding on Christ, our Paschal Lamb, and His good gifts; and let us festively banquet on him spiritually, by faith, hope, and charity, or even really in the Blessed Sacrament, and that with the unleavened bread if sincerity and truth," Cf. Chrysostom and Anselm. For though the Pascal lamb, as it was slain, was a figure of Christ slain on the Cross, yet as far as it was eaten with unleavened bread it was rather a figure of the Unbloody Sacrifice of the Eucharist. In the same way the Passover here is understood of Christ sacrificed and eaten in the Eucharist by S. Cyprian (Serm. de Cæna Dom.). by Nazianzen (Orat. de Pascha), by Chrysostom (Serm. de Pron. Juda), by Ambrose (In Luc. i.). by Jerome and Origen (in S. Matthew 26). Hence S. Andrew the Apostle said to King Ægeas: "I daily sacrifice an immaculate Lamb, which remains whole and living, even when all the people have eaten of It," Hence, too, it is that the Church reads this passage of the Apostle's for the Epistle of Easter, when she bids all to communicate and to feed on this Paschal Lamb, although in the Primitive Church the faithful ate of it daily, as the Apostle here exhorts.
Chrysostom gives us a moral meaning here when he says that we should banquet, not because it is Easter of Pentecost, but because all time is given to the Christian for so banqueting, because of the excellency of the gifts conferred. He says: "What good thing is there that the Son of God has not given you by being born and slain for you? He has set you free and called you into His kingdom. Why then do you not banquet always?" Hence S. Sylvester said that all days were festal days, because the Christian ought to feast every day, and be at leisure for God, and keep the spiritual feast. So too S. Clement of Alexandria (Strom. lib. 7) says: "The whole life of the righteous is one solemn and holy feast day."
Neither with the leaven of malice and wickedness. Vatablus translates wickedness, craftiness, and others render it depravity; for he is wicked who does evil mediately, and with guile and fraud. The Latins of old by malice and wickedness signified all the vices and crimes of men. Hence the saying of Publius Africanus (apud Gell. lib. vii. c. 11) that all the evil and disgraceful and heinous things that men do are briefly comprehended in two words, malice and wickedness.
But with the unleavened bread of sincerity and truth. A Hebraism. Let us banquet, not on literal unleavened bread, but on spiritual, i.e., on sincerity (or purity) and truth not merely truth of the mind or of the mouth, but the truth of life, the Christian righteousness; in other words, any duty of virtue that Christians are bound to, especially simplicity, faithfulness, and truth. Sincerity is here opposed to malice, and truth to wickedness. Ver. 9. I wrote unto you. In ver. 2 of this chapter. So Theodoret and Chrysostom. But S. Thomas, Lyranus, Cajetan think that S. Paul wrote this in another former epistle which has perished.
Not to company with fornicators... for then must ye needs go out of the world. When I bade you have no fellowship with fornicators I did not mean what you were to avoid fornicating pagans, for then you would have to go out of the world, for the whole world is full of pagans, who are either fornicators, or covetous, or idolaters; but if any one who is a brother, says S. Ambrose, if any one who is a Christian, is publicly spoken ill of as a fornicator, then avoid him.