Translations
But you say, "Why?" Because Yahweh was witness between you and the wife of your youth, to whom you have been faithless — she is your companion and your wife by covenant.
But you say, "For what reason?" Because YHWH was witness between you and the wife of your youth — she whom you have betrayed — your companion and your covenant wife.
Yet ye say, Wherefore? Because the LORD hath been witness between thee and the wife of thy youth, against whom thou hast dealt treacherously: yet is she thy companion, and the wife of thy covenant.
Yet you ask, “Why?” It is because the LORD has been a witness between you and the wife of your youth, against whom you have broken faith, though she is your companion and your wife by covenant.

