Mark 10:1-12
1Jesus then left that place and went into the region of Judea and across the Jordan. Again crowds of people came to him, and as was his custom, he taught them. 2Some Pharisees came and tested him by asking, "Is it lawful for a man to divorce his wife?" 3"What did Moses command you?" he replied. 4They said, "Moses permitted a man to write a certificate of divorce and send her away." 5"It was because your hearts were hard that Moses wrote you this law," Jesus replied. 6"But at the beginning of creation God 'made them male and female. 7'For this reason a man will leave his father and mother and be united to his wife, 8and the two will become one flesh. So they are no longer two, but one. 9Therefore what God has joined together, let man not separate." 10When they were in the house again, the disciples asked Jesus about this. 11He answered, "Anyone who divorces his wife and marries another woman commits adultery against her. 12And if she divorces her husband and marries another man, she commits adultery."
Malachi 2:15,16
15 Has not the LORD made them one? In flesh and spirit they are his. And why one? Because he was seeking godly offspring. So guard yourself in your spirit, and do not break faith with the wife of your youth. 16 "I hate divorce," says the LORD God of Israel, "and I hate a man's covering himself with violence as well as with his garment," says the LORD Almighty. So guard yourself in your spirit, and do not break faith.
Romans 7:1-3
1Do you not know, brothers-for I am speaking to men who know the law-that the law has authority over a man only as long as he lives? 2For example, by law a married woman is bound to her husband as long as he is alive, but if her husband dies, she is released from the law of marriage. 3So then, if she marries another man while her husband is still alive, she is called an adulteress. But if her husband dies, she is released from that law and is not an adulteress, even though she marries another man.