'Immorality' in the Bible

But I say to you that everyone who divorces his wife, except for immorality, makes her commit adultery, and whoever marries a divorced woman commits adultery.

For out of the heart come evil ideas, murder, adultery, sexual immorality, theft, false testimony, slander.

Now I say to you that whoever divorces his wife, except for immorality, and marries another commits adultery."