When princes persecute God's people, let them expect vexation on all sides. The way for any country to be quiet, is to let God's church be quiet in it: if Saul fight against David, the Philistines fight against his country. David considered himself the protector of the land. Thus did the Saviour Jesus, and left us an example. Those are unlike David, who sullenly decline to do good, if they are not rewarded for services.