21 David had just said, “It’s been useless—all my watching over this fellow’s property in the wilderness so that nothing of his was missing. He has paid me back evil for good.

Read 1 Samuel 25:21 Using Other Translations

Now David had said, Surely in vain have I kept all that this fellow hath in the wilderness, so that nothing was missed of all that pertained unto him: and he hath requited me evil for good.
Now David had said, "Surely in vain have I guarded all that this fellow has in the wilderness, so that nothing was missed of all that belonged to him, and he has returned me evil for good.
David had just been saying, “A lot of good it did to help this fellow. We protected his flocks in the wilderness, and nothing he owned was lost or stolen. But he has repaid me evil for good.