Albert Barnes Commentary 1 Samuel 22:2

"And every one that was in distress, and every one that was in debt, and every one that was discontented, gathered themselves unto him; and he became captain over them: and there were with him about four hundred men." — 1 Samuel 22:2 (ASV)

Discontented - See the margin. (Compare 1 Samuel 30:6; 2 Samuel 17:8.) The phrase here denotes those who were exasperated by Saul’s tyranny.