“Furthermore it has been said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’ 32 But I say to you that whoever divorces his wife for any reason except sexual immorality causes her to commit adultery; and whoever marries a woman who is divorced commits adultery. ~ Matthew 5:31, 32.
Jesus teaches the permanence of the marriage bond, which He says can only be broken in the case of marital unfaithfulness.
“divorces…except sexual immorality” (v.32) — The Greek word for “sexual immorality” is fairly broad, including a number of sexual sins besides adultery. In this clause (present also in 19:9 but omitted in Mark 10:11), Jesus recognizes that marital infidelity potentially destroys the marital tie between spouses and is, therefore, ground for legal divorce. However, divorce is not mandatory and reconciliation (see 18:23–35) is preferable.
“causes her to commit adultery” — The very act of divorcing a wife caused the woman to be stigmatized by the community as an adulteress whether or not she was guilty. The one remarrying her also became stigmatized. This is not a dogmatic statement referring to remarriage as being adultery