Why does Hebrews 10:5 say "a body hast thou prepared me" when Psalm 40:6 in the KJV says "mine ears hast thou opened"?

The short answer

The writer of Hebrews quotes the Psalm from the Septuagint, the Old Testament the apostles read. In the Septuagint the line reads "a body hast thou prepared me." The King James translators worked from the Masoretic text, which reads "mine ears hast thou opened" at the same place. Hebrews is not paraphrasing. It is quoting the original wording.

Psalm 39:7 LXX

“Sacrifice and offering thou wouldest not; but a body hast thou prepared me: whole-burnt-offering and [sacrifice] for sin thou didst not require.”

Psalm 40:6 KJV

“Sacrifice and offering thou didst not desire; mine ears hast thou opened: burnt offering and sin offering hast thou not required.”

What Hebrews quotes

Read Hebrews against the Septuagint and the words line up: sacrifice and offering refused, a body prepared, burnt offerings with no pleasure in them.

“Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me: In burnt offerings and sacrifices for sin thou hast had no pleasure. Then said I, Lo, I come (in the volume of the book it is written of me,) to do thy will, O God.”

Why the body matters

The whole argument of Hebrews 10 turns on that body. The sacrifices of the law were repeated year after year and never took away sins. Christ came into the world in the body the Father prepared for Him, and offered it once.

“By the which will we are sanctified through the offering of the body of Jesus Christ once for all.”

The Masoretic reading cannot carry that argument, because it never mentions a body. The Septuagint reading is the one the Holy Spirit set into the New Testament, and it points straight to the Incarnation and the cross.

Read it yourself

Open Psalm 39 in the Septuagint and Psalm 40 in the KJV side by side, or compare them in the compare view.