Jesus specifically allowed divorce for infidelity Matthew 19:9 (ESV) And I say to you: whoever divorces his wife, except for sexual immorality, and marries another, commits adultery. Note that Jesus does not say this is the only reason for divorce. We find other reasons for divorce in Scripture.

What does the Old Testament say about marriage?

Genesis 2:24: Therefore a man shall leave his father and his mother and hold fast to his wife, and they shall become one flesh. Romans 13:8: Owe no one anything, except to love each other, for the one who loves another has fulfilled the law.