Albert Barnes Commentary 1 Chronicles 5:10

"And in the days of Saul, they made war with the Hagrites, who fell by their hand; and they dwelt in their tents throughout all the [land] east of Gilead." — 1 Chronicles 5:10 (ASV)

The "Hagarites" or "Hagarenes" are generally regarded as descendants of Hagar and a distinct branch of the Ishmaelites (1 Chronicles 27:30–31; Psalms 83:6).

They appear to have been one of the wealthiest (1 Chronicles 5:21) and most widespread tribes of the Syrian Desert. They were found along the Euphrates in contact with the Assyrians, and also in the Hauran near Palestine, in contact with the Moabites and Israelites.

If they are identical with the Agraei of classical writers, their name may survive in the district called Hejer or Hejera in northeastern Arabia, on the borders of the Persian Gulf. A full account of the war is given in 1 Chronicles 5:18–22.