"Furthermore it has also been said, Whoever divorces his wife, let him give her a certificate of divorce. 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 NKJV)

whoever marries the divorced (except for sexual immorality) commits adultery

The first line of these verses reflects the permissive attitude of Old Testament Jews who were looking for a way out of an unfulfilling marriage (see Deuteronomy 24:1-4). They must have thought that God would approve their sins because they followed a legal procedure—the man gave his wife a certificate of divorce.

Easy divorce must have become even more popular because famous scholars and rabbis endorsed it. "It has been said" probably includes the permissive conclusions of rabbinical writings.

Jews had no excuse for holding erroneous views on this subject. Not only did they have the original pattern of Genesis 1-2 to guide them (as Jesus shows in Matthew 19:4-6), but also the blistering indictment against casual divorce in Malachi 2. Genesis 1-2 states the positive case for remaining married; Malachi 2 states the negative consequences of pursuing divorce.

In Matthew 5 (and Matthew 19:1-9) Jesus strongly condemns the cruel divorces so common in His day. He warns that frivolous divorce produces eternal consequences. It causes her to commit adultery. Those who marry the divorced woman also commit adultery. God’s plan always works. It is our duty to respect it. Souls are at stake.

– Rick Duggin