Charles Ellicott Commentary 2 Samuel 21:3

"and David said unto the Gibeonites, What shall I do for you? and wherewith shall I make atonement, that ye may bless the inheritance of Jehovah?" — 2 Samuel 21:3 (ASV)

Make the atonement. —This is the same technical word as is used throughout the Law in connection with the propitiatory sacrifices. It means literally, to cover up, and is here used in that literal sense. David asks what he can do to so cover up the sin of Saul as to remove it from the sight of those against whom it had been committed—the Gibeonites as the earthly sufferers from it, and God Himself as the one against whom he had chiefly offended. Then God’s blessing might again return to His people.