Albert Barnes Commentary Judges 15:3

"And Samson said unto them, This time shall I be blameless in regard of the Philistines, when I do them a mischief." — Judges 15:3 (ASV)

See the margin. Before, when the Philistines injured him, he was in covenant with the Timnathites through his marriage and by the rites of hospitality, for which reason he went off to Ashkelon to take his revenge (Judges 14:19). But now the Philistines themselves had broken this bond, and so he was free to take his revenge on the spot.