Taking the Lord's name in vain (Deut. 5:11) happens in many ways. As we have seen, this sin can refer merely to casual irreverent speech about God. However, vain use of His name can also mean cursing Him, which is the subject of today's passage.
Although every misuse of God's name is a serious sin, not every instance of blasphemy merits the same consequences. Just as the law distinguishes between first-degree murder and murder caused by carelessness (manslaughter), prescribing different punishments (Num. 35:9–34), it shows that certain forms of blasphemy are worse than others. Cursing the name of the Lord is a particularly brazen violation of the third commandment. This was particularly true when the son of Shelomith cursed God in the Israelite camp. In other words, he blasphemed in the very midst of the community among whom the Creator chose to dwell. He cursed God in a location close to the Most Holy Place (Lev. 24:10–12). Such audacity reflected a profound hardness of heart. After all, it is serious enough to curse God outside of His church, but how much more serious is it to spit on His name in His church, that is, among His holy people?
Faced with this challenge, Moses and the leaders of Israel asked God what to do. The Lord prescribed death by stoning (vv. 13–16). If this punishment seems excessively harsh to us, it likely indicates the irreverence of which we are all so often guilty. God takes His glory and honor more seriously than we do, for He is the most worthy being of all (1 Sam. 2:12–36; Heb. 3:3). Cursing Him is a grievous sin (Heidelberg Catechism, Q&A 100).
Today's passage illustrates the principle given in the third commandment that the Lord will not hold guiltless those who commit blasphemy (Deut. 5:11). Still, we must keep two things in mind when we consider what this means. First, God does not overlook any sin, so no one is held guiltless for breaking His law. That is why we need Christ, whose atonement takes care of our wickedness and allows God justly to declare us righteous before Him (Rom. 3:21–26). Second, all forms of blasphemy are forgiveable except the blasphemy of the Holy Spirit, which is the impenitent ascription of the works of the Devil to the Lord even when one knows better (Matt. 12:22–32). Those whose hearts have become so hardened as to blaspheme the Spirit, however, will never truly seek God's forgiveness.
The issue of the blasphemy of the Holy Spirit is a difficult one, but commentators agree that we have not committed this sin if we feel remorse and want God to forgive us. Only those whose hearts have been completely hardened against God and His grace have committed this sin, but we cannot determine whether this has happened in a person’s heart. Thus, we hold forth the hope of forgiveness and call people to repent until their deaths make repentance impossible.