Malachi 2:10 - Ellicott's Commentary On The Whole Bible

One father — i.e., not Adam, Abraham, or Jacob (as various commentators have held), but God Himself (Malachi 1:6; Deuteronomy 32:6; Deuteronomy 32:18), who is the spiritual Father of the nation, and in whom they are all brothers and sisters; so that when an Israelite married a heathen woman, or divorced an Israelitish wife, it was an offence against God, a “profaning the covenant of the fathers,” and a violation of the fraternal relation. Moreover, “one God created” them for His glory (Isaiah 43:7), for the special purpose of being a witness to His unity. The admission of idolatresses into their families would be fatal to this object.