What is "Netziv Pelishtim"?
'Rashi': Pelishtim had captured Beis Lechem, and established a judge there. This was at the beginning of David's kingship, when Pelishtim ruled over Yisrael, like we find in the days of Shimshon and Shmuel ? "strengthen yourselves and be valiant, Pelishtim, lest you need to serve the Ivrim" (Shmuel I, 4:9).
Rashi (Shmuel I, 13:23): They are overseers to guard lest people leave the city to despoil them.
Radak (Shmuel I, 13:23, citing Targum Yonasan): It is army officers. Bereishis Rabah (3:6) supports this.
Vilna Gaon: It is those who stand in a state of war.
Why does it say here "u'Netziv Pelishtim", and in Shmuel II, 23:14 it says "Matzav Pelishtim"?
Radak (Shmuel II, 23:14): These are the same. Also Yonason translates both of these the same. They are generals of the army. The big camp was in Emek Refa'im, and the generals and a [small] part of the army were in Beis Lechem.
