where does rashi explain a second zivug is more difficult then splitting the red see since HB volontarely does not want to know if a person os going to do mizvot and therefore does not know who belongs to who It could be it is only in Sota but i thought alos in ketubes but i can not find it anymore
nenner,
I don't believe there is such a Rashi (that says Hash-m does not "want" to know what Mitzvos the person will do in the future...). The Sugya appears in the following places: Sotah 2a, Sanhedrin 22a. In Sotah Rashi says that the difficulty of Keri'as Yam Suf is "that the orderliness of Creation was changed". Perhaps you saw someone who read into this what you wrote.
Mordecai Kornfeld
Kollel Iyun Hadaf