http://revach.net/article.php?id=4187

Section:  Avodah   Category: Olam HaTorah
Maharal MiPrague - The Magic Of Turning Leah Into Rochel
"Vayehi BaBoker ViHinei Hi Leah" (Vayeitzei 29:24).  After the controversial chasuna where Yaakov was supposed to marry Rochel the Torah tells, when the morning came, behold it was Leah.  Rashi adds, "but at night it was not Leah since Yaakov gave the Simanim to Rochel".  What does this mean that at night it was not Leah?  Then who was it?

The Maharal MiPrague tells us that from here a very powerful lesson in what it means that the Torah is the blueprint and central power of the world.  He says that the halacha is that Simanim Muvhakim are Min HaTorah.  This means that although the Chachomim decree that we can return an aveida to the person who gives simanim, nevertheless it is still not clear that the item belongs to him without a shadow of a doubt.  This can have ramifications in Halacha such as returning a lost Get or divorce.  However when a person give Simanim Muvhakim, perfect detailed and unique simanim, the gemara concludes that the item belongs to that person Min HaTotah as these simanim are conclusive.

Since Yaakov gave Rochel Simanim Muvhakim, MiDinei Torah that night the Kallah was actually Rochel as she presented the Simanim that were unique to Rochel alone.  It was only in the morning light when Leah was physically appeared before Yaakov, that Min HaTorah the Kallah was Leah!  We can learn from this Rashi and the Maharal what it means to have emuna in the Torah.