The Quran

الزّاني لا يَنكِحُ إِلّا زانِيَةً أَو مُشرِكَةً وَالزّانِيَةُ لا يَنكِحُها إِلّا زانٍ أَو مُشرِكٌ ۚ وَحُرِّمَ ذٰلِكَ عَلَى المُؤمِنينَ

Muhammad Asad

[Both are equally guilty:] the adulterer couples with none other than an adulteress - that is, a woman who accords [to her own lust] a place side by side with God;¹ and with the adulteress couples none other than an adulterer - that is, a man who accords [to his own lust] a place side by side with God: and this is forbidden unto the believers.²

The term mushrik (fem. mushrikah), which normally signifies a person who associates in his or her mind all manner of imaginary deities or forces with God, or who believes that any created being has a share in His qualities or powers, is here evidently used in the widest metaphorical sense of this term, denoting one who accords to his or her desires a supremacy which is due to God alone, and thus blasphemes against the principles of ethics and morality enjoined by Him. The particle aw (lit., "or") which connects the word mushrikah with the preceding word zanjyah ("adulteress") has in this context - as well as in the next clause, where both these terms appear in their masculine form - an amplifying, explanatory value equivalent to the expression "in other words" or "that is", similar to the use of this particle in 23:6. For a further elucidation of the above passage, see next note.
Some of the commentators understand this passage in the sense of an injunction: "The adulterer shall not marry any but an adulteress or a mushrikah; and as for the adulteress; none shall marry her but an adulterer or a mushrik." This interpretation is objectionable on several counts: firstly, the Qur'an does not ever countenance the marriage of a believer, however great a sin he or she may have committed, with an unbeliever (in the most pejorative sense of this term); secondly, it is a fundamental principle of Islamic Law that once a crime has been expiated by the transgressor's undergoing the ordained legal punishment (in this case, a hundred stripes), it must be regarded, insofar as the society is concerned, as atoned for and done with; and, lastly, the construction of the above passage is clearly that of a statement of fact (Razi), and cannot be interpreted as an injunction. On the other hand, since adultery is an illicit sexual union, the verb yankihu, which appears twice in this passage, cannot have the customary, specific meaning of "he marries" but must, rather, be understood in its general sense - applicable to both lawful and unlawful sexual intercourse - namely, "he couples with". It is in this sense that the great commentator Abu-Muslim (as quoted by Razi) explains the above verse, which stresses the fact that both partners are equally guilty inasmuch as they commit their sin consciously - implying that neither of them can excuse himself or herself on the ground of having been merely "seduced".