dealt treacherously - namely, in respect to the Jewish wives who were put away (Mal 2:14; also Mal 2:10, Mal 2:15, Mal 2:16).
profaned the holiness of ... Lord - by ill-treating the Israelites (namely, the wives), who were set apart as a people holy unto the Lord: “the holy seed” (Ezr 9:2; compare Jer 2:3). Or, “the holiness of the Lord” means His holy ordinance and covenant (Deu 7:3). But “which He loved,” seems to refer to the holy people, Israel, whom God so gratuitously loved (Mal 1:2), without merit on their part (Psa 47:4).