John Calvin Commentary Matthew 5:32

"but I say unto you, that every one that putteth away his wife, saving for the cause of fornication, maketh her an adulteress: and whosoever shall marry her when she is put away committeth adultery." — Matthew 5:32 (ASV)

Causeth her to commit adultery. As the bill of divorcement bore, that the woman had been loosed from her former husband, and might enter into a new marriage, the man who, unjustly and unlawfully, abandons the wife whom God had given him, is justly condemned for having prostituted his wife to others.