Komentaryo sa Genesis 15:8: Kli Yakar, Sforno, Kitzur Ba'al HaTurim & Radak

“How shall I know that I will inherit it?” Our Sages said (Nedarim 32) that because Abram said “How shall I know,” he was punished with [the decree] Know with certainty [that your offspring shall be strangers in a land not theirs, and they shall be enslaved and oppressed four hundred years]; and logic would refuse to accept this interpretation that his children should suffer such a great punishment because of the sign that Abram requested, while Abram himself received no punishment and [only] his children’s teeth were set on edge. Therefore, my heart tells me and concludes that the Egyptian exile had other causes, and our Sages disagreed about this, and you can find all the opinions in the Abarbanel, as he gathered them together. Indeed, the length of this single sheet is too short to record all those opinions. However, the author of this midrash found it difficult: Whatever the reason for the exile may be, why did the Holy One, Blessed be He, tell this bad news to Abram to cause him unnecessary pain? To this he answered that because of the sin of saying How shall I know, where he wanted to know something that there was no need to know — for why should he seek a sign for God’s word — therefore he was punished with Know with certainty where the Holy One, Blessed be He, informed him of something [distressing] to cause him pain, and this too was measure for measure.

במה אדע, for possibly my descendants will sin and forfeit their claim to this land.

"What will I know?" In the context of the prohibition of the Torah. Blessed be His name, the conversation of Isaac arrived at the calculation of 400, and therefore a decree of 400 was decreed upon his children. "What will I know" in the calculation, that two years were added at the end of the years when no man passed in Judah, and seventy were in exile.