Mismated translates a word meaning “yoked with another of a different kind.” Paul may have had in mind the admonition of Deut 22.10, which forbids plowing with an ox and a donkey yoked together. In what way the Christians are not to be yoked together is not stated. Good News Translation interprets this as working together. Possibly it refers to marriage, but this meaning is probably too limited in this context. The verb occurs only here in all the New Testament. But a related word is found in Phil 4.3, where it is translated “yokefellow.” Other translations of the verb here have rendered it “harness yourselves in an uneven team with” (New Jerusalem Bible) and “consent to be yokefellows” (Knox). The verb and the negation are together translated in Contemporary English Version as “stay away from…,” by Moffatt as “keep out of all incongruous ties with…,” and elsewhere as “refuse to be united with….”
Unbelievers refers to persons who are not Christians. More specifically, in the context between appeals to the Corinthians to be reconciled to Paul, he possibly has in mind his opponents in the church at Corinth, who have rejected his apostolic authority. In areas where Islam is strong, translators must pay careful attention to the meaning of the word for unbelievers, since it is very likely to carry the meaning of “non-Muslim.” In such cases it is better to use an expression like “people who do not believe in Christ.”
Partnership … fellowship: these two words are different in Greek but virtually synonymous in meaning in this context. The first is used only here in the New Testament and comes from an expression for having something together with someone else. The related verb form occurs in 1 Cor 9.10, 12; 10.21. The second occurs frequently—especially to describe the close association believers have with each other (Acts 2.42 and Gal 2.9) or the fellowship of believers with Christ (1 Cor 1.9). Its basic meaning is that several people share a common feature or common activity, and this binds them in a special unity.
Righteousness: in Paul’s writings the word righteousness usually refers to being put right with God, but here the sense seems to be that of right conduct. See also the comments on this term at 3.9 and 5.21.
Iniquity: this same term is translated elsewhere in RSV as “wickedness” (Matt 24.12) and “lawlessness” (2 Thes 2.7; Heb 1.9; 1 John 3.4). It carries the basic meaning of illegality or violation of God’s laws and stands in radical opposition to righteousness both here and in Rom 6.19. Since these two terms are abstract, some languages will require that they be personified by talking about “a righteous person” or “righteous people” on the one hand and “an evil person” or “evil people” on the other.
Light and darkness, as with righteousness and iniquity, express opposites. Here light and darkness are used metaphorically to refer to moral qualities or to belief and unbelief (see Rom 13.12; Eph 5.11-14; 1 Thes 5.5). In some languages it may be necessary to use the words for “daylight” and “night” to express these two figures of speech.
The two questions in this verse are rhetorical questions. The implicit reply to both questions is that there is certainly no partnership, no fellowship. God’s New Covenant retains the question form but adds the word “why?” to the first question; such an addition in English clearly suggests that a negative response is implied: “Why, what kinship is there between righteousness and lawlessness?” In languages where the rhetorical nature of these questions may not be recognized, translators may need to restructure and express these two questions as emphatic statements. Others will possibly express the idea as follows: “a righteous person and an evil person cannot agree with each other, and light cannot unite with darkness. Is this not true?”
Quoted with permission from Omanson, Roger L. and Ellingworth, Paul. A Handbook on Paul’s Second Letter to the Corinthians. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .