John Lightfoot on Matthew 5:32

[Whosoever shall put away his wife, &c.] I. Our Saviour does not abrogate Moses' permission of divorces, but tolerates it, yet keeping it within the Mosaic bounds, that is, in the case of adultery, condemning that liberty in the Jewish canons, which allowed it for any cause.

II. Divorce was not commanded in the case of adultery, but permitted. Israelites were compelled, sometimes even by whipping, to put away their wives, as appears in Maimonides (Gerushin). But our Saviour, even in the case of adultery, does not impose a compulsion to divorce, but indulgeth a license to do it.

III. "He that puts away his wife without the cause of fornication makes her commit adultery": that is, if she commits adultery: or although she commit not adultery in act, yet he is guilty of all the lustful motions of her that is put away; for he that lustfully desires, is said "to commit adultery," verse 28.