sexual immorality . . . immorality: The Greek word por·neiʹa, used twice in this verse, is a general term for all sexual activity that is unlawful according to the Bible. It includes adultery, prostitution, sexual relations between unmarried individuals, homosexual acts, and bestiality.​—See Glossary.

hand such a man over to Satan: This was a command to expel, or disfellowship, a man from the congregation. (1Co 5:13; 1Ti 1:20) The man would then become part of the world over which Satan is the god and ruler. (1Jo 5:19) The person’s expulsion would result in the destruction of the flesh, or the removal of the corrupting element from the congregation. As a result, the congregation’s positive spirit, or dominant attitude, would be preserved.​—2Ti 4:22.

leaven: Or “yeast.” Often used figuratively in the Bible to denote corruption and sin, here referring to corrupt teachings.​—Mt 16:12; 1Co 5:6-8; compare study note on Mt 13:33.

leaven: Or “yeast.” A substance added in order to ferment dough; especially a portion of fermented dough preserved from a previous batch. (Ex 12:20) In the Bible, leaven is often used as a symbol of sin and corruption.​—See study note on Mt 16:6.

ferments: Or “spreads through; affects.” The Greek verb used here, zy·moʹo (“to leaven”), is related to the noun for “leaven,” zyʹme, also used in this verse. At Ga 5:9, Paul uses the same metaphor, which was apparently a proverbial saying.

Clear away the old leaven: Paul here draws on the symbolic meaning of the Jewish Festival of Unleavened Bread, which immediately followed the Passover celebration. During the Passover, the Israelites removed any leaven from their houses. Similarly, Christian elders needed to act to get “the old leaven” out of the midst of the congregation. (1Co 5:8) Just as a bit of leaven, or sourdough, soon causes the whole batch of dough to ferment, so a corrupt person could influence the whole congregation, making it unclean in Jehovah’s eyes.

you are free from ferment: Lit., “you are unleavened.” (See Glossary, “Festival of Unleavened Bread.”) Leaven often represented sin and wickedness, so Paul compares the pure, unblemished life course of Christians to observing the Festival of Unleavened Bread.​—1Co 5:8; see study note on Clear away the old leaven in this verse.

Christ our Passover lamb has been sacrificed: In Israel, Nisan 14 was the joyous day of the Passover celebration. Each year on that day, families shared a meal that included a young, unblemished lamb. Christians did not celebrate the Passover. However, that meal reminded them of the vital role that the lamb’s blood played in saving the Israelite firstborn on Nisan 14, 1513 B.C.E. At that time, God’s angel of death killed every firstborn of the Egyptians but spared those of the obedient Israelites. (Ex 12:1-14) Paul here shows that the Passover lamb foreshadowed Jesus. Jesus died on Nisan 14, 33 C.E. Like the blood of the Passover lamb, Jesus’ shed blood provides salvation for many.​—Joh 3:16, 36.

the congregation of God that is in Corinth: Paul founded the Corinthian congregation about 50 C.E. (Ac 18:1-11) While in Ephesus about 55 C.E., Paul wrote this first inspired letter to the Corinthians. (Compare 1Co 5:9.) The brothers in Corinth had recently written to Paul, asking questions about marriage and the eating of foods offered to idols. (1Co 7:1; 8:1) But Paul was aware of problems that were even more pressing. The congregation was tolerating a case of flagrant immorality. (1Co 5:1-8) And there were also divisions in the congregation. (1Co 1:11-13; 11:18; 15:12-14, 33, 34) There may also have been some uncertainty about the proper handling of the Lord’s Evening Meal. (1Co 11:20-29) Paul provided inspired direction on these matters, placing special emphasis on the importance of showing Christian love.​—1Co 13:1-13.

In my letter I wrote you: Paul is clearly referring to an earlier letter that he wrote to the Corinthians, one that we do not possess today. God apparently chose not to preserve the earlier letter, possibly because it was essential only to those to whom it was addressed.​—See study note on 1Co 1:2.

stop keeping company with: Or “stop associating with.”​—See study note on 1Co 5:11.

sexually immoral people: This expression renders the Greek noun porʹnos, which is related to the noun por·neiʹa (sexual immorality, 1Co 5:1) and the verb por·neuʹo (to practice sexual immorality, 1Co 6:18). (See Glossary, “Sexual immorality.”) From ancient times, Corinth was known as a place where people had a morally decadent lifestyle and worshipped the goddess Aphrodite. That worship promoted sensuality and immorality. (Compare study note on 1Co 7:2.) Paul indicates that some Christians in Corinth had previously led an immoral lifestyle but had changed their conduct and were now good associates.​—1Co 6:11.

the prevalence of sexual immorality: This expression renders the plural form of the Greek word por·neiʹa. Some translations render the opening phrase: “Because sexual immorality is so common [or, “rampant”].” This well describes the situation in ancient Corinth.​—See study note on 1Co 5:9.

stop keeping company with: Or “stop associating with.” The Greek word sy·na·na·miʹgny·mai, rendered “keeping company with,” means “to mix up together.” (The same Greek verb occurs at 2Th 3:14.) Thus, “keeping company” with others would imply having close fellowship or companionship with them and sharing their views and sentiments. Christians in Corinth had to “stop keeping company with,” that is, refuse to mingle with, any unrepentant sinner. They were to “remove the wicked person from among [themselves].”​—1Co 5:13.

the sexually immoral people: See study note on 1Co 5:9.

sexually immoral people: This expression renders the Greek noun porʹnos, which is related to the noun por·neiʹa (sexual immorality, 1Co 5:1) and the verb por·neuʹo (to practice sexual immorality, 1Co 6:18). (See Glossary, “Sexual immorality.”) From ancient times, Corinth was known as a place where people had a morally decadent lifestyle and worshipped the goddess Aphrodite. That worship promoted sensuality and immorality. (Compare study note on 1Co 7:2.) Paul indicates that some Christians in Corinth had previously led an immoral lifestyle but had changed their conduct and were now good associates.​—1Co 6:11.

stop keeping company with: Or “stop associating with.” The Greek word sy·na·na·miʹgny·mai, rendered “keeping company with,” means “to mix up together.” (The same Greek verb occurs at 2Th 3:14.) Thus, “keeping company” with others would imply having close fellowship or companionship with them and sharing their views and sentiments. Christians in Corinth had to “stop keeping company with,” that is, refuse to mingle with, any unrepentant sinner. They were to “remove the wicked person from among [themselves].”​—1Co 5:13.

who is sexually immoral: See study note on 1Co 5:9.

a reviler: Or “a verbally abusive person.” A reviler is a person who regularly insults others with the intention of hurting them. A person who refuses to stop reviling is not qualified to be part of the congregation.​—1Co 5:11-13; 6:9, 10.

not even eating with such a man: With this phrase, Paul further clarified what he meant when he said “to stop keeping company with” those in the congregation who unrepentantly carry on sinful activities. In the Bible, eating together was often a sign of friendship and led to further association. Jewish Christians understood this very well, since Jews did not keep company with or eat with people “of the nations.”​—Mt 18:17; Ac 10:28; 11:2, 3.

sexually immoral people: This expression renders the Greek noun porʹnos, which is related to the noun por·neiʹa (sexual immorality, 1Co 5:1) and the verb por·neuʹo (to practice sexual immorality, 1Co 6:18). (See Glossary, “Sexual immorality.”) From ancient times, Corinth was known as a place where people had a morally decadent lifestyle and worshipped the goddess Aphrodite. That worship promoted sensuality and immorality. (Compare study note on 1Co 7:2.) Paul indicates that some Christians in Corinth had previously led an immoral lifestyle but had changed their conduct and were now good associates.​—1Co 6:11.

Remove the wicked person from among yourselves: At the beginning of this chapter, Paul gave instructions to remove from the congregation, or to disfellowship, a man who was living a sexually immoral life. (1Co 5:1, 2; see study notes on 1Co 5:1, 5.) Citing his authority for such instruction, Paul here quotes Jehovah’s law to Israel: “Remove what is bad from your midst.” (De 17:7) The quote is apparently taken from the Septuagint, which reads “the wicked (evil) person” instead of “what is bad (wicked; evil).” Similar exhortations can be found at De 19:19; 22:21, 24; 24:7.

sexual immorality . . . immorality: The Greek word por·neiʹa, used twice in this verse, is a general term for all sexual activity that is unlawful according to the Bible. It includes adultery, prostitution, sexual relations between unmarried individuals, homosexual acts, and bestiality.​—See Glossary.

hand such a man over to Satan: This was a command to expel, or disfellowship, a man from the congregation. (1Co 5:13; 1Ti 1:20) The man would then become part of the world over which Satan is the god and ruler. (1Jo 5:19) The person’s expulsion would result in the destruction of the flesh, or the removal of the corrupting element from the congregation. As a result, the congregation’s positive spirit, or dominant attitude, would be preserved.​—2Ti 4:22.