Murder is a most grievous sin. Once we get past the common evangelical error that all sins are equally wicked we recognize that murder will surely be one of the biggest sins. After all, we are told those who practice these things will not see the kingdom of heaven (Gal. 5:21). That said, however, we know of at least two men guilty of murder who are in heaven, David, and Paul. The list in Galatians 5 is not a list of unforgivable sins. Instead it is a list of those sins, which when they are practiced, evidence a lack of saving faith. Practicing these sins, however, is not the same thing as committing them. We practice these sins, or any sin, when we give up, when we no longer fight the temptation, when we embrace the sin as good. When, however, we fight, when we repent for falling into these sins, He is faithful and just to forgive us our sins (1 John 1:9).
R.C. Sproul Jr.