John Calvin Commentary Exodus 23:13

"And in all things that I have said unto you take ye heed: and make no mention of the name of other gods, neither let it be heard out of thy mouth." — Exodus 23:13 (ASV)

Make no mention of the name of other gods. There is no doubt that this declaration should be connected with the Third Commandment. Moses explains that God’s name is taken in vain and abused if people swear by other gods, for it is not lawful to refer the judgment of unknown things to any other than the one true God.

Consequently, the glory of the Deity is transferred to those by whose name people swear. Therefore, by the Prophet, God pronounces a severe denunciation that He will destroy all those who swear by His name and also by Malcham (Zephaniah 1:5), since in this way the Jews mixed Him with their idol and so profaned His holiness.

In sum, since by swearing we profess that He is our God—whom we declare to be both the knower of our hearts and the judge of our souls—the true God justly claims this honor for Himself alone, because the glory of His name is diminished, not only if we speak less reverently of Him than we should, but also if we associate with Him any who might usurp a part of His rights.

And this appears more clearly from the two passages we have cited from Deuteronomy, in which the people are commanded to swear by the name of the one God. This is equivalent to rendering to His sacred name, in our outward profession of service, the unmixed reverence it deserves.³¹¹

Still, God does not exhort the people to freely indulge in oaths, as if by frequent oaths they were practicing duties of piety. He simply means that when there is an occasion or necessity for it, and a just cause shall demand it, they must swear in no other way than by invoking Him alone as their witness and judge.

³¹¹ “Ce qui vaut autant comme de luy rendre l’hommage qu’il merite, en le constituant tesmoin des choses cachees, et confessant que c’est a luy seul de maintenir la verite;” which is equivalent to rendering to Him the homage He deserves, in constituting Him the witness of hidden things, and confessing that it is His alone to maintain the truth. — ;” which is equivalent to rendering to Him the homage He deserves, in constituting Him the witness of hidden things, and confessing that it is His alone to maintain the truth. — Fr.