Albert Barnes Commentary 1 Samuel 30:28

"and to them that were in Aroer, and to them that were in Siphmoth, and to them that were in Eshtemoa," — 1 Samuel 30:28 (ASV)

Aroer - This is not Aroer on the Arnon, but (if the name is written correctly) some town in Judah that is not named elsewhere.

Siphmoth, Rachal (1 Samuel 30:29), and Athach (1 Samuel 30:30) are unknown and not mentioned elsewhere. However, Zabdi the Shiphmite (1 Chronicles 27:27), who was in charge of David’s wine cellars, was evidently a native of Siphmoth.

It is a remarkable proof of David’s grateful nature and his faithfulness to his early friendships—as well as a curious instance of undesigned coincidence—that we find so many inhabitants of those obscure places where he found friends during his early difficulties employed by him in positions of trust at the height of his power.

Ezri the son of Chelub, Shimei the Ramathite, and Zabdi the Shiphmite, as well as Ira, Gareb, Ittai, Hezrai, and many others, were probably among these friends from his youth.