2 Corinthians 6:14

Μὴ γίνεσθε ἑτεροζυγοῦντες κ. τ. λ.: be not (mark that the pres. tense γίνεσθε indicates the beginning of a state, sc., “do not become”) unequally yoked with unbelievers, the constr. being “be not unequally yoked, as you would be if you were yoked with unbelievers”. The most obvious application of such a prohibition would be to intermarriage with the heathen, which was continually forbidden to the chosen people (see Deuteronomy 7:3; Joshua 23:12; Ezra 9:2; Nehemiah 13:25), and this is probably the main thought here (see ref. Lev. for ἑτερόζυγος); but to indulge in any excessive familiarity of intercourse would be “to be enlarged in heart” in a way which the Apostle strongly deprecates (cf. 1Ma 1:15). He enforces this by five contrasts which illustrate the incongruity between Christianity and heathendom. τίς γὰρ μετοχὴ κ. τ. λ.: for what fellowship have righteousness and lawlessness? or what communion has light with darkness? Cf. Ephesians 5:7, μὴ οὖν γίνεσθε συμμέτοχοι αὐτῶν · ἦτε γάρ ποτε σκότος, νῦν δὲ φῶς ἐν Κυρίῳ, and cf., for the same image, Acts 26:18; Romans 13:12; 1 Thessalonians 5:5 and chap. 2 Corinthians 4:6; 2 Corinthians 11:14.