Charles Ellicott Commentary 1 Samuel 26:15

"And David said to Abner, Art not thou a [valiant] man? and who is like to thee in Israel? wherefore then hast thou not kept watch over thy lord the king? for there came one of the people in to destroy the king thy lord." — 1 Samuel 26:15 (ASV)

A valiant man.—The English translators have rightly emphasized the Hebrew ish here by rendering a “valiant” man. Ish was often used in this “nobler” sense, as in Psalms 49:2, where the b’ne adam, as “the poor mean ones,” were contrasted with the b’ne ish, “the noble ones.” (See also Isaiah 2:9: mean men and great men).

Wherefore then hast thou not kept?—The whole of this bitter sarcastic address seems to imply that a deadly feud existed between David and Saul’s captain and kinsman, Abner. If this is the case, the royal generosity and nobility of David’s character was well shown in his subsequent friendship with this Abner, and in his deep sorrow for the great captain’s untimely death. (See 2 Samuel 3).