David, with characteristic Oriental subtlety (compare 1 Samuel 21:2), suggests as a reason for leaving Gath that his presence was burdensome and expensive to the king. His real motive was to be more out of the way of observation and control, so as to act the part of an enemy of Saul, without really lifting up his hand against him and his own countrymen of Israel.
Related Commentaries of 1 Samuel 27:5
1 Samuel 27:5
5 And David said unto Achish, If I have now found grace in thine eyes, let them give me a place in some town in the country, that I may dwell there: for why should thy servant dwell in the royal city with thee?