1 Corinthians 6:18

6:18 Flee sexual immorality! “Every sin a person commits is outside of the body” ¹  – but the immoral person sins against his own body.

1 Corinthians 11:27

11:27 For this reason, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of the body and blood of the Lord.

1 Corinthians 12:23

12:23 and those members we consider less honorable we clothe with greater honor, and our unpresentable members are clothed with dignity, ² 

[6:18]  ¹ sn It is debated whether this is a Corinthian slogan. If it is not, then Paul is essentially arguing that there are two types of sin, nonsexual sins which take place outside the body and sexual sins which are against a person’s very own body. If it is a Corinthian slogan, then it is a slogan used by the Corinthians to justify their immoral behavior. With it they are claiming that anything done in the body or through the body had no moral relevance. A decision here is very difficult, but the latter is to be preferred for two main reasons. (1) This is the most natural understanding of the statement as it is written. To construe it as a statement by Paul requires a substantial clarification in the sense (e.g., “All other sins…” [NIV]). (2) Theologically the former is more difficult: Why would Paul single out sexual sins as more intrinsically related to the body than other sins, such as gluttony or drunkenness? For these reasons, it is more likely that the phrase in quotation marks is indeed a Corinthian slogan which Paul turns against them in the course of his argument, although the decision must be regarded as tentative.

[12:23]  ² tn Grk “have greater propriety (or decorum, presentability).”