The gemorah says that if a navi is a muchzak, then you don't need a sign that he is a navi. One of the proofs that the gemorah brings is from the akeidah.Yitzchok did not need a sign to do what Avrohom said because Avrohom was muchzak as a Navi.
However, before when the gemorah talks about withholding a prophecy, the gemorah says the way we would know, is because other neviim had the same prophecy. So my question is what kind of proof, about the requirement of a sign, is it from Yitzchok? Yitzchok was also a navi! So maybe the reason why he didn't need to ask for a sign from Avrohom was because he had the same prophecy? So maybe you really can't prove this from the akeida?
SG, Brooklyn, NY
This that other Nevi'im have the same prophecy applies only to a prophecy that is intended to be said over. It is also by these prophecies that there is a law of "Kovesh Neva'so." In contrast, the Nevu'ah to Avraham was a personal one.
In addition, it is clear from the question of "Ayeh ha'Seh" that Yitzchak was unaware at that point.