When Delilah asked Shimshon where his miraculous strength came from, he gave four responses:
- tie me up with seven moist ropes
- no, they have to be NEW, THICK ropes
- put seven of my hairs into a loom
- cut off my hair
She did each one, as he was sleeping. After the fourth one, he had violated his nezirus, and was punished by losing his strength.
My question is as follows:
Jumping up with your hair tied into a loom definitely has the consequence of those hairs being torn out of your head. According to Rashi Shabbos 50b, the halachos of psik reisha apply to Nazir as well as to Shabbos*. Therefore, jumping up with the loom should have been an active violation of his nezirus.
On the other hand, the fourth time, he didn't actively do anything - Delilah was the one who cut his hair while he was sleeping, and if he had been awake he probably would have objected. It's not obvious to me that this is forbidden on a Torah level, and the relevant derabbanans most likely hadn't been introduced yet.
For all these reasons, the third time should have been a worse violation of his nezirus.
It didn't actually turn out that way, because Hashem made a miracle and his hairs had supernatural strength. But He could have made the same miracle when Delilah cut his hair and just made her fail. Why did Hashem miraculously prevent Shimshon from actively violating his nezirus but not from passively violating it?
* Tosfos disagrees with Rashi about the particulars of the case in that Gemara and says that the problem there is davar hamiskavein rather than psik reisha (some discussion here), but it's not clear that he disagrees with the application of psik reisha to a Nazir in other cases - such as trying to lift up a loom by the strength of 7 hairs.