While the name of God is used comprehensively to refer ultimately to God Himself, the phrase translated in vain means ‘falsely’ (cf. Is. 59:4). The word translated ‘taketh’ means ‘to bear’ or ‘carry,’ as believers bear or carry His name when they are called Christians. But of course if we cannot live in a false manner under His name, still less may we speak or swear falsely in His name. So the verse bluntly excludes false oaths. ‘Thou shalt not swear (utter) the name of God to emptiness (vanity).’ Simply put, we should refrain from appealing to the name of God to confirm or bear witness to a falsehood. When we appeal to God by means of vows, we must honor God by honoring our vows. In the eyes of God, vows are serious business.
Douglas Wilson