John Gill

Thou shall not take the name of the Lord God in vain,.... Make use of the name Lord or God, or any other name and epithet of the divine Being, in a light and trifling way, without any show of reverence of him, and affection to him; whereas the name of God ought never to be mentioned but in a grave and serious manner, and with an awe of the greatness of his majesty upon the mind. The Targums of Onkelos and Jonathan restrain this to swearing by the name of the Lord; and so the Jewish writers generally interpret it either of swearing lightly, rashly, or falsely; and to this it may very well be extended, though not limited; and so forbids, as all profane oaths; imprecations, and curses by the name of God, which the mouths of wicked men are full of, so swearing by it in matters trivial, and of no importance; for swearing even by the name of the Lord ought not to be used but in matters of moment and consequence, for the confirmation of a thing, and putting an end to strife, and where a matter cannot be determined and decided without an appeal to God. And great care should be taken that a man swears to that which is true, and not false; for false swearing, or perjury, is a very grievous sin, and as it is strictly forbidden, it is severely punished by the Lord, as follows; see Lev 19:12, this is the third command, and the reason enforcing it follows: for the Lord will not hold him guiltless that taketh his name is vain; will not look upon him as an innocent person, and treat him as such; will not acquit and discharge him as just and righteous; but on the contrary will consider him as a guilty person, a profaner of his name, and a transgressor of his law, and will condemn and punish him, if not in this world, yet in the world to come; and so the Targum of Jonathan, by way of explanation, adds,"in the day of the great judgment;''see Mal 3:5.