What does Hebrews 9:28 mean?

The context of this verse is the often-quoted verse 27, which indicates that each man experiences a single death and subsequent judgment by God. A major advantage to the new covenant promised by God is the fact that Christ's sacrifice does not need to be repeated over and over, as the animal sacrifices do. Animal blood can only temporarily atone for sin, and cannot change man from the inside. The sacrifice of Christ, however, completely saves from sin, as a "once for all" action. In the prior verse, this was compared to the way in which men die a single time, and that this death leads to judgment.

Here, the writer of Hebrews points out that Christ appeared once, and died once, and this death was for the purpose of judgment on sin. This means His Second Coming, which is yet in the future, will not result in an additional atonement. Just as each man dies once, Christ will only die for sins once. Just as men die, and then are judged, Christ has already died, and will return only to judge the world. Christ's next arrival will be for the purpose of "saving" those who have trusted in Him. This is meant in the sense that Christ's ultimate return, in victory, signals the final completion of God's plan to judge sin and save His people (Titus 2:13).