Glossa Ordinaria

(non occ.) The Lord has hitherto taught to abstain from injuring our neighbour, forbidding anger with murder, lust with adultery, and the putting away a wife with a bill of divorce. He now proceeds to teach to abstain from injury to God, forbidding not only perjury as an evil in itself, but even all oaths as the cause of evil, saying, Ye have heard it said by them of old, Thou shall not forswear thyself. It is written in Leviticus, Thou shalt not forswear thyself in my name; (c. 19:12.) and that they should not make gods of the creature, they are commanded to render to God their oaths, and not to swear by any creature, Render to the Lord thy oaths; that is, if you shall have occasion to swear, you shall swear by the Creator and not by the creature. As it is written in Deuteronomy, Thou shall fear the Lord thy God, and shall swear by his name. (c. 6:13.)