I use ordinary words (Jerusalem Bible “if I may use human terms”; New American Bible “I use the following example from human affairs”) is the same expression used in 3.5, I speak here as men do, and is best taken as a reference to what Paul is going to say. The equivalent might very well be “let me use an ordinary example” or “let me use an example from everyday life.”
Paul’s use of the phrase the weakness of your natural selves is not intended here to have moral or ethical implications; it is only a reference to the fact that he believes these people incapable of understanding profound truths unless he uses analogies from everyday life. The phrase is literally “the weakness of your flesh”; it appears in the New American Bible as “your weak human nature” and in the Jerusalem Bible as “your natural weakness.” The New English Bible combines the two phrases: “to use words that suit your human weakness.”
It is important to avoid, in the choice of a word for weakness, an expression which will apply only to physical weakness. In fact, it may be necessary to qualify “weakness” as “weakness of your understanding” or “weakness of the way in which you, as just a human being, understand things.”
Yourselves entirely appears twice in verse 13 and is there translated first by any part of yourselves and then by your whole being.
Impurity and wickedness (literally “lawlessness”; in 4.7 translated wrongs) were two sins that the Jews generally accused the Gentiles of committing. The idea of wickedness is made emphatic in this verse by being used twice (wickedness, for wicked purposes). The word rendered impurity is used also in Romans 1.24 (there rendered filthy things). Paul also uses the word in 2 Corinthians 12.21; Galatians 5.19; Ephesians 4.19; 5.3; Colossians 3.5; 1 Thessalonians 2.3; 4.7. Outside of Paul’s writings it appears only in Matthew 23.27.
Slaves to impurity and wickedness may be rendered as “slaves to do what is impure and wicked” or “slaves to do what is sexually and generally bad.” “Sexually and generally” are simply ways of designating the focal components of impurity and wickedness.
Since purpose has already been expressed in relating wickedness to slaves, it is often difficult to add a further purpose (for wicked purposes), which is merely an emphatic amplification of the term wickedness. One may, therefore, translate wickedness as “to do all kinds of wickedness.”
Holy purposes (New English Bible “a holy life”) appears in Moffatt and An American Translation* as “consecration” and is a word that is normally rendered “sanctification” or “holiness” in most translations. It appears in Paul’s writings here and in 6.22; 1 Corinthians 1.30; 1 Thessalonians 4.3, 4, 7; 2 Thessalonians 2.13; 1 Timothy 2.15; and outside Paul’s writings in Hebrews 12.14 and 1 Peter 1.2. Basically the idea involved in this word is that of being dedicated or set aside to God, and in other than Jewish and Christian contexts the words has no connotation of purity of life. However, in biblical thought purity of life does become basic because the people who are set aside for the service of God are expected to take on the likeness and character of God. So in the present context the idea is either that of being set aside to God for the sake of achieving his holy purposes (Good News Translation) or for the sake of “making for a holy life” (New English Bible). Attention should be called to the fact that the adverb now stands emphatic in the second sentence of this verse.
As in verse 18, slaves of righteousness may be translated as “slaves to do what is right.”
The final phrase for holy purposes may be rendered as an explanation of righteousness—for example, “that is to say, to do that which is holy.” But if one adopts the meaning of “consecration,” it may be rendered better as “this is in order that you may be truly God’s people” or “in order that you may be really dedicated to God.”
Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on Paul’s Letter to the Romans. (UBS Handbook Series). New York: UBS, 1973. For this and other handbooks for translators see here .