Mark 10:11
He answered, anyone who divorces his wife and marries another woman commits adultery against her — the private clarification makes the implication explicit: divorce and remarriage constitutes adultery. Against her is significant — in Jewish law, adultery was committed against the husband of the woman involved; Jesus' formulation that the man commits adultery against his own wife (the one he divorced) is a novel framing that extends marital fidelity obligations to the man.