"Whoever divorces his wife and marries another commit adultery; and whoever marries her who is divorced from her husband commits adultery" (Luke 16:18; NKJV).
According to Jesus, there is one exception to the general rule of Luke 16:18.
"And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery" (Matthew 19:9; NKJV).