What does Matthew 19:7 mean?

Attempting to trip Jesus up and discredit Him, some Pharisees have asked Him a question about His stance on divorce. Is it lawful for a man to divorce his wife for any and every reason? Jesus has responded by quoting Genesis. This shows that marriage was designed at creation by God even before sin entered the world. God made us male and female. When a man and woman marry, God joins them together making them one flesh. What God has joined, men should not separate, Jesus has said (Matthew 19:1–6).

Now the Pharisees push back. They like to cite Scripture, but not all of it. In this case, Jesus is not using the passage they usually talked about concerning divorce. They point out to Jesus that Moses' commands allowed husbands to give their wives a certificate of divorce and send them away.

The divorce text the Pharisees want to talk about is found in Deuteronomy 24:1–4. The law contained in those verses describes a scenario in which a man gives his wife a certificate of divorce because he finds some "indecency" in her, and he sends her out of his house. The point of the command is that a specific man is not allowed to re-marry that specific woman if she marries another man first. That remarriage after an in-between marriage is described as an abomination to the Lord.

So the law does not specifically address under what circumstances divorce is allowed, but it does show that divorce was practiced among the Israelites during Moses' time. The Pharisees want to know how that fits with what Jesus just said about not separating what God has joined.