Samson does not take the Judahites at their word that they will simply bind him and hand him over to the Philistines. He evidently thinks they may want to attack and strike him themselves. To suffer death at the hands of his own people would be far more shameful than death at the hands of the enemy, even if at the hands of a woman (recall Judges 4:21; Judges 9:54). Samson would rather be killed by the enemy.1
12 And they said to him, “We have come down to bind you, that we may give you into the hands of the Philistines.” And Samson said to them, “Swear to me that you will not attack me yourselves.”