Old Testament readings use the Septuagint , the Scripture the apostles quoted. Masoretic numbering shown for reference.Learn why
LXX

2 Samuel 21:2

And king David called the Gabaonites, and said to them;—(now the Gabaonites are not the children of Israel, but [are] of the remnant of the Amorite, and the children of Israel had sworn to them: but Saul sought to smite them in his zeal for the children of Israel and Juda.)

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