What the Bible actually says about divorce depends entirely on which book you read and which author you might refer to.
The Old Testament refers to divorce and certificates of divorce, and appears to allow it mainly as a fix for when couples have been unfaithful to each other. Bible Study Tools quotes Deuteronomy (Chapter 24 Verse 1 and 4): "If a man marries a woman who becomes displeasing to him because he finds something indecent about her, and he writes her a certificate of divorce, gives it to her and sends her from his house... then her first husband, who divorced her, is not allowed to marry her again..."
Bible Study Tools also includes quotes from the New Testament, including Mark 10:2-12 where the Pharisees ask Jesus to interpret Moses' law on divorce. This is when Jesus is quoted as saying, "For this reason a man will leave his mother and father and united to his wife and the two will become one flesh... Therefore what God has joined together, let no one separate."
But Matthew further explains the Old Testament's stand on divorce in Chapter 19 (Verses 8-9) saying: "Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning. I tell you that anyone who divorces his wife, except for sexual immorality, and marries another woman commits adultery."
