Chapter 25 — Part III: The Decalogue — The Second Commandment
Section 35. An Objection Against Oaths — Nor does this doctrine at all clash with these words of the Redeemer, recorded in St. Matthew: You have heard that it was said to them of old: "Thou shalt not foreswear thyself, but thou shalt perform thy oaths to the Lord"; but I say to you not to swear at all; neither by heaven, for it is the throne of God; neither by the earth, for it is his footstool; nor by Jerusalem, for it is the city of the great king; neither shalt thou swear by thy head, because thou canst not make one hair white or black. But let your speech be "yea, yea"; "no, no"; and that which is over and above these is of evil.