1 Chronicles 12:19

12:19 Some men from Manasseh joined David when he went with the Philistines to fight against Saul. (But in the end they did not help the Philistines because, after taking counsel, the Philistine lords sent David away, saying: “It would be disastrous for us if he deserts to his master Saul.”)

1 Chronicles 14:8

14:8 When the Philistines heard that David had been anointed king of all Israel, all the Philistines marched up to confront him. When David heard about it, he marched out against them.