BartholomewB:
Ah, now I’m beginning to catch up with you. Are you saying the same as @stpurl, that the husband and wife were not legitimately married to begin with?
I think we have to assume that Jesus recognized that it was a valid marriage as he specifically addresses the couple as husband and wife and not as fornicators. The OT is clear that a previously married woman may not go back to her ex-husband even if the ex-husband is willing to, if she had remarried after her divorce. Because she has been defiled. Deu 24:1-5.
The Matthew verses are interesting because it did not prohibit divorce per se, but prohibit remarriage. This reinforces the point that Jesus made in that initially man/woman are joined as one. But if the wife were to be unchaste, the man is no longer bound to her as she has been defiled and the union has been broken as Deu 24 indicates. If there is no unchastity involved, both the man or the woman can not remarry because it results in adultery as the union remains valid in God’s eyes. Sure one can divorce but not remarry. Unfortunately during Mosaic days, women is considered as chattel, and usually requires subsistence support from the males which always end up in them having to remarry in order to survive. The hardness of the heart as Jesus put it. Also in those days where wars are frequent, the women also ended up as widows with no one to take care as they do not get any inheritance, especially if they are without sons. But that was revoked upon appeal eventually Numbers 27.