What does Hebrews 10:14 mean?

Sacrifices under the old covenant had to be repeated over and over. This, according to the writer of Hebrews, is a deliberate aspect of the old covenant, as ordained by God (Hebrews 9:6–10). These animal sacrifices could temporarily cover human sin, but could not remove it. This repetition, along with other aspects of the old covenant, was meant to point us towards Jesus Christ, who fulfilled the new covenant. That new covenant was promised, by God, to be something different from the Levitical priesthood, and anchored inside the hearts and minds of the people (Hebrews 8:7–13).

Recently, the writer of Hebrews has been specifically referring to repetitive animal sacrifice, which is inferior to the single sacrifice given by Jesus Christ. Psalm 40 was quoted to show that God Himself contrasted offerings and sacrifices with the use of a "body" to accomplish His will. The work Jesus did on the cross, then, becomes the fulfillment of that promise.

The use of the term "perfected" here should be taken in the usual biblical context: as a reference to maturity and completion. This is not a reference to sinlessness, since even Jesus—who had no sin (Hebrews 4:15)—is said to be "perfected" in a sense by God as He performed the Father's will (Hebrews 2:10). Instead, this echoes the idea presented in Hebrews 7:25: that Christ's sacrifice can do, completely, what the animal sacrifices of the old covenant could only do partially.