Many have difficulty understanding exactly what the church is because many have a poor understanding of what God's temple is. This has in a large way been caused by their not having been taught the proper interpretation of singular and plural Koine' Greek pronouns, such as are well divided in the KJV (not the NKJV which failed to carry this feature over).
In the KJV, the translators faithfully used thee, thou, thy, and thine to denote singular Greek pronouns. And, in the KJV, the translators faithfully used ye, you, your, and yours to denote plural Greek pronouns.
In other Bible versions this is accomplished by different methods, however, not all, like the NKJV, even bother to highlight this difference. That is a bit of a disservice to the reader because then they must struggle more to understand what they have read or look up the pronouns to determine whether they were singular of plural.
Why is this important? 1 Corinthians 3:16 "Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?"
Now, many read that and being unaware of the KJV's method of highlighting plural pronouns interpret "ye" as singular. They thus think that Paul is referring to their personal body of flesh. However, he is not meaning that. He is speaking to the group as the collective one body of Christ, which he describes in greater detail at Ephesians 2: 14-22.
There also in Ephesians, just before explaining more clearly what the temple of God is, Paul says, Ephesians 2:10 "For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them."
We find that he explained those good works in more detail there in 1 Corinthians 3:6-11. Paul taught all who joined to Christ's body to be busy bringing others to Christ.
They thus were all busy bringing yet others into the church, even some whose faith was the quality of wood, hay, and stubble. Many of these wood, hay and stubble ones lacked in true appreciation for spiritual things and were there more for social reasons or to make a show of their intelligence. That is why Paul warned, 1 Corinthians 3:13 "Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is." And Paul warned, 1 Corinthians 3:17-19 "If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are. Let no man deceive himself. If any man among you seemeth to be wise in this world, let him become a fool, that he may be wise. For the wisdom of this world is foolishness with God. For it is written, He taketh the wise in their own craftiness."
And only two chapters later we find this: 1 Corinthians 5:1 "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 wife. And ye are puffed up, and have not rather mourned, that he that hath done this deed might be taken away from among you."
Why was that important? 1 Corinthians 5:6-8 "Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump? 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 and truth."
Their failure to be on guard against allowing such corruption to reside in Christ's body would hinder God's spirit among the, as God will not dwell in the presence of unholiness.
1 Corinthians 5:4-5 "In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ, 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."
That is speaking about destroying the flesh out of the church that God's spirit might be saved among them. It has nothing to do with trying to help the sinner at this point.
The church needs to understand that the flesh is to be left as dead with Christ at Calvary. It cannot be allowed to yet live among the body, else it makes a mockery of Christ as though he died to become a shelter for sin.