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

1 Samuel 15:15

And Saul said, I have brought them out of Amalec, that which the people preserved, even the best of the sheep, and of the cattle, that it might be sacrificed to the Lord thy God, and the rest have I utterly destroyed.

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