For seven days they are to make atonement for the altar and cleanse it; thus they will dedicate it.
NIV
For seven days shall they make atonement for the altar and purify it; so the priests shall consecrate, separate, and set it apart to receive offerings. [Exod. 29:37.]AMP
Seven days shall they purge the altar and purify it; and they shall consecrate themselves.
KJV
