Chapter 25 — Part III: The Decalogue — The Second Commandment
Section 17. To swear by creatures, such as the holy Gospels, the cross, the names or relics of the Saints, and so on, in order to prove our statements, is also to take an oath Of themselves, it is true, such objects give no weight or authority to an oath; it is God Himself who does this, whose divine majesty shines forth in them Hence to swear by the Gospel is to swear by God Himself, whose truth is contained and revealed in the Gospel (This holds equally true with regard to those who swear) by the Saints, who are the temples of God, who believed the truth of His Gospel, were faithful in its observance, and spread it far and wide among the nations and peoples.