There is, in fact, only one case in the New Testament where a divorce was contemplated. However, there was a happy ending. The couple were reconciled and the divorce did not take place.

The story, of course, is that of Joseph and Mary. Joseph's belief that Mary's child was conceived as the result of fornication led to his mistaken decision to divorce her.

This decision by Joseph was a quite "legally" proper one, in the light of the Law of Moses. A girl who had been seduced was obliged to marry the man who had seduced her ...... unless her father refused. (Ex. 22:16-17)

Thus Joseph was not legally entitled to take Mary as his wife, if it was in fact true that she ought to marry another. It was only after God made it clear to Joseph that there was no other man that Joseph became free to continue with the marriage.

As well as being the only Gospel to record "fornication" as the sole cause for divorce, Matthew is also the only one to mention that Joseph was about to divorce Mary for that reason.

Matthew's inclusion of "fornication" as the single exception to the general rule that all other divorce is forbidden allows us to understand that Joseph was reacting exactly as might be expected of a righteous and just man, obedient to the Law of Moses. Joseph was also in harmony with the mind of God in the matter, as it was later taught by Jesus.

Jesus was not giving any approval at all for divorce of those already validly joined by God. Rather he was talking about the separation of an improper union which God had not joined.

The real meaning of "fornication" as the only possible ground for divorce was something which had touched the life of those closest to Jesus, very deeply. Years later, the supposed scandal of his birth by fornication was thrown up to him by the Pharisees, as an excuse to reject him. (John 8:41)

For us, the story not only adds to our understanding of the subject of divorce, but it is also a proof of Joseph's belief in the Virgin Birth. If Joseph had not believed the dream in which God revealed that to him, he would have gone ahead with the divorce. "Fornication", if it had really existed, would have prevented the union of Joseph and Mary being valid in God's sight because of the prior claim of another man. Instead, Joseph believed God and continued with the marriage.