Someone has recently told me that the fruit of the Tree of Knowledge eaten by Adam and Eve was not an apple. Is this correct?
The Talmud cites three opinions:
Rabbi Meir says that the Tree of Knowledge was a grapevine—"for nothing causes more heartbreak than wine...."
Rabbi Nehemiah maintains that it was a fig tree. The Torah tells us that after the sin, Adam and Eve "knew that they were naked, and they sewed fig leaves and made themselves girdles." Rabbi Nehemiah maintains that "that which caused their downfall, was then used to rectify them."
Rabbi Judah says it was actually wheat stalks! He bases his contention on the fact that "a child knows not how to call out to his father and mother until he has tasted grain." As such, the Tree of Knowledge was actually grain.
The Midrash quotes another opinion, that the fruit of the Tree of Knowledge was an etrog (citron).
Another opinion cited in the Midrash is that "G‑d did not disclose the identity of the tree's species, and He never will." This in order to protect the honor of a species that would otherwise be tarnished—through no fault of its own.
Rabbi Naftali Silberberg,
Chabad.org Editorial Team