Jamieson, Fausset and Brown on 1 Samuel 15:6

6. Kenites--(See on Jud 1:16). In consequence, probably, of the unsettled state of Judah, they seem to have returned to their old desert tracts. Though now intermingled with the Amalekites, they were not implicated in the offenses of that wicked race; but for the sake of their ancestors, between whom and those of Israel there had been a league of amity, a timely warning was afforded them to remove from the scene of danger.

1Sa 15:7-9. He Spares Agag and the Best of the Spoil.