Matthew 19:9

And I say unto you,.... To his disciples, when they were with him alone in the house, and asked him more particularly about the subject, concerning which he had been discoursing with the Pharisees, as Mark observes, Mark 10:10 when he said to them much the same things, he had delivered before in Matthew 5:32

whosoever shall put away in his wife; separate her from his person, house and bed, and dismiss her as his wife, no more to be considered in that relation to him,

except it be for fornication; or whoredom, for defiling his bed: for this is not to be understood of fornication committed before, but of uncleanness after marriage, which destroys their being one flesh:

and shall marry another woman, committeth adultery; Marks adds, "against her"; which may be understood either of the woman he marries, which not being lawfully done, she lives in adultery with the husband of another woman; or of his former wife, and who is still his wife, and to whose injury he has married another; and he not only commits adultery himself, but, as in Matthew 5:32 "causeth her to commit adultery also", by being the occasion of marrying another man, when she is still his lawful wife:

and whoso marrieth her which is put away, for any other cause than adultery,

doth commit adultery also; since he cohabits with the wife of another man; see Gill "Mt 5:32"