2 Samuel 21:2

the Amorites Amorites(highlanders) is here and elsewhere used as a general designation for the ancient inhabitants of Palestine, particularly those who occupied the mountainous country. See note on 1 Samuel 7:14. The Gibeonites belonged to the tribe of the Hivites.

had sworn unto them See Joshua 9:3 ff. The oath though obtained by fraud was acknowledged to be binding (Joshua 9:19-20), and its violation was a breach of the third commandment (Exodus 20:7).

in his zeal Probably in a fit of zeal to carry out the Law by cleansing the land from the remnant of the heathen (Exodus 34:11-16; Deuteronomy 7:2) as he cleansed it from the soothsayers (1 Samuel 28:3). There is no allusion to the deed elsewhere.

wherewith shall I make the atonement The cognate substantive also rendered satisfaction(Numbers 35:31) and ransom(Exodus 30:12) means literally a covering. The "atonement" is a covering, which hides the offence from the eyes of the offended party, and withdraws the guilt from the gaze of an avenging God.