God is serious about marriage. Christ here, (Christ who is the exact representation of God’s being) and in other places of scripture, says that if we divorce our spouse, we cause them to commit adultery. It’s not that they committed adultery. But if you divorce them, it causes or makes them to commit adultery. If they were sexually immoral, they have already committed adultery. But if you divorce them, even though they’ve not committed sexual immorality, then you make them to commit adultery – even if they don’t commit adultery in the future.