1 Samuel 27:5 - Ellicott's Commentary On The Whole Bible

Why should thy servant dwell in the royal city with thee? — The real reason why David wished a separate residence was that he might conduct his forays and other affairs apart from the supervision of his Philistine friends. They had one purpose in welcoming him and his band, he had quite another. Achish trusted that through David’s assistance powerful military demonstrations in the southern districts of Saul’s kingdom might be made. At this time the Philistine nation were preparing for that grand national effort against Saul which culminated in the battle of Mount Gilboa. David, on the other hand, intended, from a comparatively secure centre of operations somewhere in Philistia, to harry those nomad foes of Israel whose home was in the deserts to the south of Canaan.