(5) Mortify therefore your members which are upon the earth. — The expression is doubly unique. It is the only passage where “mortification” — the killing of anything in us — is enjoined; and it is also notable, as not explicitly distinguishing between the members themselves, and the evil of which they are made the instruments. The sense is, of course, clear enough. It corresponds to the “crucifying the flesh” of Galatians 5:24; and the idea of evil, mostly expressed plainly in the word “flesh,” is here hinted in the phrase “which are on the earth,” that is, which are busied with earth and bind us down to the earthly life. The particular word “members” is perhaps suggested by our Lord’s command to “cut off the right hand” and “pluck out the right eye” if they cause us to offend (Matthew 5:29-30). But, as a rule, Scripture more clearly marks the distinction between the members and “the law of sin in the members” (Romans 7:5; Romans 7:23); and we are usually bidden not to “kill our members,” but to turn them from “instruments of unrighteousness” to be “instruments of righteousness unto God” (Romans 6:13). The fact is that this passage contains only half the truth, corresponding to the death with Christ, and not the whole truth, including also the resurrection to the new life. Accordingly, as the next verse shows, the members to be mortified are actually identified with the vices of the old man residing in them.
Fornication, uncleanness... covetousness, which is idolatry. — See Ephesians 5:3, and Note there.
Inordinate affection, evil concupiscence. — These words are not found in the parallel passage. The word rendered “inordinate affection” is the general word for “passion” (pathos). It is found united to “concupiscence” in 1 Thessalonians 4:5, “the lust of concupiscence.” Both words here are general words, denoting the condition of soul, of which “fornication” and “covetousness” are both exemplifications. This is the condition of unrestrained passion and desire, the former word implying a passive receptiveness of impression from without, the other the positive energy of desire to seek gratification. Comp. Galatians 5:24, “the affections” (passions) and “lusts.” Of such a temper Article IX. of the Church of England declares with singular accuracy, not that it is sin, but that it has in itself rationem peccati, that is, the initial principle of sin.