And Pharisees came up and in order to test him asked, “Is it lawful for a man to divorce his wife?” He answered them, “What did Moses command you?” They said, “Moses allowed a man to write a certificate of divorce, and to put her away.” But Jesus said to them, “For your hardness of heart he wrote you this commandment. But from the beginning of creation, ‘God made them male and female.’ ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh.’ So they are no longer two but one flesh. What therefore God has joined together, let not man put asunder.”
–Mark 10:2-9