Seventh. We are agreed as follows concerning the oath: The oath is a confirmation among those who are quarreling or making promises. In the Law it is commanded to be performed in God’s Name, but only in truth, not falsely. Christ, who teaches the perfection of the Law, prohibits all swearing to His [followers], whether true or false, – neither by heaven, nor by the earth, nor by Jerusalem, nor by our head, – and that for the reason which he shortly thereafter gives, for you are not able to make one hair white or black. So you see it is for this reason that all swearing is forbidden: we cannot fulfill that which we promise when we swear, for we cannot change [even] the very least thing on us. Now there are some who do not give credence to the simple command of God, but object with this question: Well, now did not God swear to Abraham by Himself (since He was God) when He promised him that He would be with him and that He would be his God if he would keep His commandments, – why then should I not also swear when I promise to someone? Answer: Hear what the Scripture says: God, since He wished more abundantly to show unto the heirs the immutability of His counsel, inserted an oath, that by two immutable things (in which it is impossible for God to lie) we might have a strong consolation. Observe the meaning of this Scripture: What God forbids you to do, He has the power to do, for everything is possible for Him. God swore an oath to Abraham, says the Scripture, so that He might show that His counsel is immutable. That is, no one can withstand nor thwart His will; therefore He can keep His oath. But we can do nothing, as is said above by Christ, to keep or perform [our oaths]: therefore we shall not swear at all [nichts schweren].
Then others further say as follows: It is not forbidden of God to swear in the New Testament, when it is actually commanded in the Old, but it is forbidden to swear by heaven, earth, Jerusalem and our head. Answer: Hear the Scripture, He who swears by heaven swears by God’s throne and by Him who sitteth thereon. Observe: It is forbidden to swear by heaven, which is only the throne of God: how much more is it forbidden [to swear] by God Himself! Ye fools and blind, which is greater, the throne or Him that sitteth thereon.
Further some say, Because evil is now in the world, and because man needs God for [the establishment of] the truth, so did the apostles Peter and Paul also swear. Answer: Peter and Paul only testify of that which God promised to Abraham with the oath. They themselves promise nothing, as the example indicates clearly. Testifying and swearing are two different things. For when a person swears he is in the first place promising future things, as Christ was promised to Abraham Whom we a long time afterwards received. But when a person bears testimony he is testifying about the present, whether it is good or evil, as Simeon spoke to Mary about Christ and testified, Behold this (child) is set for the fall and rising of man in Israel, and for a sign which shall be spoken against.
Christ also taught us along the same line when He said, ‘Let your communication be Yea, yea; Nay, nay, for whatsoever is more than those cometh of evil.’ He says, ‘Your speech or word shall be yea and nay.’ (However) when one does not wish to understand, he remains closed to the meaning. Christ is simply Yea and Nay, and all those who seek Him simply will understand His word. Amen.