Menno Simons on ... the swearing of oaths
We are aware that the magistracy claim and say, We are allowed to swear when justice is on our side. This we simply answer with the word of the Lord. To swear truly was allowed to the Jews under the law; but the gospel forbids this to christians. [p. 273]
Christ says, Ye have heard that it hath been said by them of old time, Thous shalt not forswear thyself, but shalt perform unto the Lord thine oaths; But I say unto you, Swear not at all; neither by heaven; for it is God's throne: Nor by the earth: for it is his footstool, etc., Matt. 5:33-35. And you, Micron, say that nothing but lightminded, false oaths are hereby prohibited, as if Moses allowed Israel to swear lightminedly and falsely; and that Christ, under the New Testament only forbade it; notwithstanding that all intelligent readers know that it was not merely allowed Israel to swear truly, but also commanded them to do so, Lev. 19:12; Deut. 10:20.
If the Israelites, then, had the same liberty in this matter that we
have, as you have it, and if it be such a glorious thing and honor to
God rightly to swear by the name of God, as you dare boldly lie against
your God, then tell me why the wisdom did not say, You have heard that
it hath been said to them of old, thoud shalt not forswear thyself, thus
I say, Thou shalt do likewise? while he says, Moses commanded not to forswear
thyself, but I say unto you, Thou shalt not swear at all. [p. 409]
All excerpts are from The complete works of Menno Simon (Elkhart, Ind., 1871).