I hear there are fornicators among you
(one of you is having sex with his stepmother)
It is reported commonly that there is fornication among you, and such fornication as is
not so much as named among the Gentiles, that one should have his father's
And ye are puffed up, and have not rather mourned, that he that hath done
this deed might be taken away from among you.
I've heard that there are fornicators among you. 
One of you even had sex with his stepmother.
For I verily,
as absent in body, but present in spirit, have judged already, as though
I were present, concerning him that hath so done this deed,
In the name of our Lord Jesus Christ, when ye are gathered together, and
my spirit, with the power of our Lord Jesus Christ,
I've already judged him. 
Give him to Satan (to save his soul)
To deliver such an one
unto Satan for the destruction of the flesh, that the spirit may be
saved in the day of the Lord Jesus.
Your glorying is not good. Know ye not that a little leaven leaveneth the
He should be given to Satan to destroy his body
so that his spirit may be saved when Jesus returns.
Purge out therefore the old leaven, that ye may be a new lump, as ye are
unleavened. For even Christ our passover is sacrificed for us:
Therefore let us keep the feast, not with old leaven, neither with the
leaven of malice and wickedness; but with the unleavened bread of sincerity
Our passover lamb is Christ,
who was sacrificed for us. 
Shun fornicators (and other wicked people)
I wrote unto you in an epistle not to company
In a previous epistle, 
I told you not to associate with fornicators.
Yet not altogether with the fornicators of this world, or with the
covetous, or extortioners, or with idolaters; for then must ye needs go out
of the world.
I wasn't referring to fornicators who are nonbelievers,
because then you'd have to stay away from everyone.
But now I have written unto you not to keep company, if any man that is
called a brother be a fornicator, or covetous, or an idolater, or a railer,
or a drunkard, or an extortioner; with such an one no not to eat.
But you must shun all fornicators, idolaters, and drunkards who are believers.
Don't even share a meal with them. 
For what have I to do to
judge them also that are without? do not ye judge them that are within?
Why should we judge nonbelievers?
Isn't it only believers that we should judge? 
But them that are without God judgeth. Therefore put away from among yourselves that wicked
God will judge the nonbelievers.
But you must shun wicked people.
- It is reported commonly that there is fornication among you. (v.1)
Paul, judging from rumors alone, complains
that there are fornicators among his followers in Corinth; he is even worried
that some have had sex with their fathers' wives. He says that those who have
done these things should be "delivered to Satan for the destruction of the flesh" so that their
soul can be saved.
Is it wrong to have sex outside of marriage?
- I ... have judged already. (v.3)
To judge or not to judge
- Christ our passover is sacrificed for us. (v.7)
Does God approve of human sacrifices?
- I wrote unto you in an epistle. (v.9)
Despite its title, First Corinthians wasn't the first epistle that Paul wrote the Corinthians. There was another
(Zeroth Corinthians?) that was either lost or considered not worthy of including in the Bible.
- With such an one no not to eat (v.11)
Stay away from fornicators, idolaters, and drunkards.
Do not associate, speak to, or eat dinner with such "wicked" people.
Jehovah's Witnesses use these verses to justify disfellowshipping those who fail to follow
the teachings of the Governing Body. JWs are told to
shun disfellowshipped family and friends. They are not to speak to them or share a
meal with them. If a witness is caught doing so, they will be disfellowshipped as well.
- Do not ye judge them that are within? (v.12)
To judge or not to judge
- Purge out the old leaven and become a new lump.
- Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. 5:7
- Don't eat or associate with the wicked children of disobedience.
- I wrote unto you in an epistle not to company with fornicators. Yet not altogether with the fornicators of this world, or with the covetous, or extortioners,
or with idolaters; for then must ye needs go out of the world. But now I have written unto you not to keep company, if any man that is called a brother be a
fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one no not to eat. ...
Put away from among yourselves that wicked person. 5:9-13