A moment of ultimate betrayal unfolds as a long-guarded secret is finally surrendered. After multiple failed attempts to uncover the source of Samson's strength, the truth is laid bare. Delilah immediately understands that he has finally revealed his true secret. The primary approach among commentators is that she recognized his sincerity simply because words of truth carry a distinct, undeniable weight [רש״י, מצודת דוד, ביאור שטיינזלץ].
However, several specific reasons explain why she was so certain this time. First, Samson invoked the name of God, declaring himself a Nazirite. Delilah knew he would never use the divine name falsely [רד״ק, ביאור שטיינזלץ], especially since she had personally witnessed him observing Nazirite customs [מצודת דוד]. Furthermore, his explanation shifted dramatically. In previous encounters, he merely claimed that certain bindings would weaken him. Now, he openly addressed the actual root of his power, stating clearly that his strength would physically depart from him [רד״ק]. He also provided complete answers to both of her lingering questions, explaining exactly what made him so strong and precisely how he could be subdued. By admitting that he would lose his power even if someone else shaved his head, he removed any doubt that he was lying [מלבי״ם].
Convinced of her success, Delilah summons the lords of the Philistines, urging them to come up just one more time to deliver her payment [מצודת דוד]. She emphasizes that they should come this time because the Philistine leaders had grown frustrated by her previous failures and had stopped visiting her [מלבי״ם].
The narrative captures this urgency through a subtle shift between the written text and how it is traditionally read aloud [מנחת שי]. The written form represents the voice of the messenger informing the Philistines that Samson had told his secret to her. Meanwhile, the spoken reading preserves Delilah's direct quote, as she commanded the messenger to tell them that Samson had finally opened his whole heart to me [רד״ק].
Hearing this, the Philistines respond to her call. They arrive with the promised silver in their hands [מצודת דוד], fully confident that she has at last uncovered his true secret [ביאור שטיינזלץ].