KJV:
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.
NASB:
"Yet you say, 'For what reason?' Because the LORD has been a witness between you and the wife of your youth, against whom you have dealt treacherously, though she is your companion and your wife by covenant.