Although many people believe taking the Lord's name in vain refers to using the Lord's name as a swear word, there is much more involved with a vain use of God's name. To understand the severity of taking the Lord's name in vain, we must first see the Lord's name from His perspective as outlined in Scripture. The God of Israel was known by many names and titles, but the concept embodied in God's name plays an important and unique role in the Bible. God's nature and attributes, the totality of His being, and especially His glory are reflected in His name (Psalm 8:1). Psalm 111:9 tells us His name is "holy and awesome," and the Lord's prayer begins by addressing God with the phrase "hallowed be your name" (Matthew 6:9), an indication that a reverence for God and His name should be foremost in our prayers. Too often we barge into God's presence with presumptuous "to-do lists" for Him, without being mindful of His holiness, His awesomeness, and the vast chasm that separates our nature from His. That we are even allowed to come before His throne is due only to His gracious, merciful love for His own (Hebrews 4:16). We must never take that grace for granted.
Because of the greatness of the name of God, any use of God's name that brings dishonor on Him or on His character is taking His name in vain. The third of the Ten Commandments forbids taking or using the Lord's name in an irreverent manner because that would indicate a lack of respect for God Himself. A person who misuses God's name will not be held "guiltless" by the Lord (Exodus 20:7). In the Old Testament, bringing dishonor on God's name was done by failing to perform an oath or vow taken in His name (Leviticus 19:12). The man who used God's name to legitimize his oath, and then broke his promise, would indicate his lack of reverence for God as well as a lack of fear of His holy retribution. It was essentially the same as denying God's existence. For believers, however, there is no need to use God's name to legitimize an oath as we are not to take oaths in the first place, letting our "yes be yes" and our "no be no" (Matthew 5:33-37).
However, there is a larger sense in which people today take the Lord's name in vain. Those who name the name of Christ, who pray in His name, and who take His name as part of their identity, but who deliberately and continually disobey His commands, are taking His name in vain. Jesus Christ has been given the name above all names, at which every knee shall bow (Philippians 2:9-10), and when we take the name "Christian" upon ourselves, we must do so with an understanding of all that signifies. If we profess to be Christians, but act, think, and speak in a worldly or profane manner, we take His name in vain. When we misrepresent Christ, either intentionally or through ignorance of the Christian faith as proclaimed in Scripture, we take the Lord's name in vain. When we say we love Him, but do not do what He commands (Luke 6:46), we take His name in vain and are in danger of hearing Him say to us, "I never knew you. Depart from me" in the day of judgment (Matthew 7:21-23).
The name of the Lord is holy, as He is holy. The name of the Lord is a representation of His glory, His majesty, and His supreme deity. We are to esteem and honor His name as we revere and glorify God Himself. To do any less is to take His name in vain.