Charles Ellicott Commentary 2 Samuel 15:18

"And all his servants passed on beside him; and all the Cherethites, and all the Pelethites, and all the Gittites, six hundred men that came after him from Gath, passed on before the king." — 2 Samuel 15:18 (ASV)

Cherethites ... Pelethites. —See Note on 2 Samuel 8:18.

Gittites. —This word in its form would naturally mean men of Gath, and it has therefore been understood by some commentators as a body of Philistines in David’s service. But the term is distinctly explained here as meaning the six hundred men which came after him from Gath, and called “Gittites” for that reason, a body of men with whom the previous history of David has made us very familiar.

They had gathered to him during his outlawry (1 Samuel 22:1–2), had been with him at Keilah (1 Samuel 23:13), in the wilderness of Paran (1 Samuel 25:13), and at Gath (1 Samuel 27:3). They came after him from Gath to Ziklag, and shared with him in his life and exploits there (1 Samuel 27:8; 1 Samuel 29:2; 1 Samuel 30:1–9). These men also went up with him to Hebron (2 Samuel 23:0) and from there to Jerusalem (2 Samuel 5:6).

They are generally supposed to have afterwards constituted the body of “heroes” or “mighty men,” to whom frequent reference is made (2 Samuel 10:7; 2 Samuel 16:6; 2 Samuel 20:7; 1 Kings 1:8). The Vatican Septuagint here, as often, adds considerably to the text.