Question:If a person marries a person who had been divorced but not for a scriptural reason though he presented himself as having a scriptural reason for divorce and so they marry. Then later, the innocent party finds out that the one party did not in fact have scriptural reason for divorce. What then? Does he leave his wife and children? This should tell the young and single to really know their mate before marrying. It seems tough to be held responsible for your partner's deception.
Let me start with the last point first. We take our promises far too lightly. When the Gibeonites sent emissaries to Joshua (Joshua 9:3-27), they disguised themselves to make it look as if they had come from a distant country. The people made a treaty with them and only afterwards learned that the people of Gibeon were in the territory that they were supposed to conquer. Despite the fact that the oaths were based on deception, the Israelites kept their promises. As God warns, our word must be kept, even if it is to our own hurt. David describes a righteous man as one "who swears to his own hurt and does not change" (Psalm 15:4). It is always important, but it becomes critical for promises made to God. "Do not be rash with your mouth, and let not your heart utter anything hastily before God. For God is in heaven, and you on earth; therefore let your words be few" (Ecclesiastes 5:2). Therefore, claims of being deceived is not enough of an excuse to separate ourselves from the consequences of promises we have made.
If a person makes a covenant of marriage with another, but it was fraudulent because the other person had no right to marry, then the relationship is adulterous. "So then if, while her husband lives, she marries another man, she will be called an adulteress" (Romans 7:3). That is why Jesus stated, "whoever marries a woman who is divorced commits adultery" (Mathew 5:32). The solution is to end the adulterous marriage.
Yes, it is hard. Some find it impossible to put living righteously before their spouse. That is why Jesus stated, "All cannot accept this saying, but only those to whom it has been given: For there are eunuchs who were born thus from their mother's womb, and there are eunuchs who were made eunuchs by men, and there are eunuchs who have made themselves eunuchs for the kingdom of heaven's sake. He who is able to accept it, let him accept it" (Matthew 19:11-12). Because of mistakes some have to accept a life of chastity in order to live in accordance with God's teachings.
But leaving doesn't mean they are absolved of all responsibility either. If children are involved, they are still responsible for their care and upbringing. If their spouse is dependant on their support, they still owe them care.