What does Hebrews 10:13 mean?

The writer of Hebrews has been very careful to support all of his claims using the Old Testament. The original audience of this letter was persecuted Jewish Christians. These believers needed to be reminded that accepting Christ did not mean rejecting their faith; it meant fulfilling it. One of the highlight Scriptures used earlier in this letter was Psalm 110:1, which not only mentions the "right hand," but also the idea of making Messiah's enemies His footstool.

In the prior verses of Hebrews, the writer reiterated how the sacrifices of the old covenant could not truly cleanse man from sin. They could temporarily delay judgment, but not permanently remove sin (Hebrews 9:6–10). Christ's sacrifice, on the other hand, is the single, once-for-all-time payment which completely saves us from our sins (Hebrews 9:11–12). While priests have to offer an imperfect sacrifice over and over (Hebrews 10:1–2), Christ offered His single sacrifice, and then "sat down," symbolizing His finished work (Hebrews 10:12).