The redemption

"When told by Hashem to go to Mitzrayim and take out Bnei Yisroel, Moshe Rabbeinu asks Hashem why Bnei Yisroel will believe that Hashem sent him. Hashem tells him to tell them "Pakod Pakaditi" (I have surely remembered) which is the Siman(sign) of the true Go'el(redeemer) that was passed down from Yosef throughout the generations. The Ramban asks, if everyone knew this siman then it wasn't much of a secret, so what guaranteed the integrity of the person saying it. Anyone can say it even an impostor?
He gives two answers. First that part of Hashem's promise for the geula and the simanim was that no impostors would come. The first one that would come would be the true Go'el.
Another answer he says is that this is the reason Moshe was cut off from his father's house. Had he grown up by Amram, they would not have believed him, and they would have thought he knew the siman from his father. Growing up in Paroh's palace and being exiled from Mitzrayim at a young age gave him credibility when he arrived fresh on the scene with the long awaited sign."
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