Matthew 19:6

Wherefore they are no more twain
They were two before marriage, but now no more so; not but that they remain two distinct persons,

but one flesh;
or, as the Syriac, Arabic, Persic, and Ethiopic versions read, "one body": hence the wife is to beloved by the husband as his own body, as himself, as his own flesh, ( Ephesians 5:28 Ephesians 5:29 ) .

what therefore God hath joined together;
or, by the first institution of marriage, has declared to be so closely united together, as to be, as it were, one flesh, and one body, as husband and wife are;

let no man put asunder;
break the bond of union, dissolve the relation, and separate them from each other, for every trivial thing, upon any slight occasion, or for anything; but what is hereafter mentioned. The sense is, that the bond of marriage being made by God himself, is so sacred and inviolable, as that it ought not to be dissolved by any man; not by the husband himself, or any other for him; nor by any state or government, by any prince or potentate, by any legislator whatever; no, not by Moses himself, who is, at least, included, if not chiefly designed here, though not named, to avoid offence: and God and man being opposed in this passage, shows, that marriage is an institution and appointment of God, and therefore not to be changed and altered by man at his pleasure; this not merely a civil, but a sacred affair, in which God is concerned.