Charles Ellicott Commentary 1 Samuel 15:6

"And Saul said unto the Kenites, Go, depart, get you down from among the Amalekites, lest I destroy you with them; for ye showed kindness to all the children of Israel, when they came up out of Egypt. So the Kenites departed from among the Amalekites." — 1 Samuel 15:6 (ASV)

And Saul said to the Kenites. —The Kenites, like the Amalekites, were a nomad race of Arabs, but seem to have been always friendly to the Israelites. This kindly feeling sprang up soon after the departure from Egypt, and was, no doubt, initially because Hobab, Moses' father-in-law, belonged to this people.