Samson went and caught three hundred foxes, and took firebrands, and turned tail to tail, and put a firebrand in the midst between every two tails.
It is not exactly clear what the purpose of the Philistines was in burning Samson's wife and her family with fire.  To us, it seems quite unlikely that they were taking Samson's part and executing a penalty provoked by their treatment of Samson.  It seems rather, that they simply BLAMED the Timnathite family for being the original cause of the firing of the grain fields, and treated them accordingly.  In any case, Samson did not appreciate what they did, and proceeded to slaughter a great number of them.  His immediate retirement to the cleft in the rock of Elam indicates that he probably thought the incident was concluded.  He had promised "to cease" when his revenge was complete.