Was Eliyahu similar to Moshe, who did not eat or drink for 40 days on Har Sinai?
1.
Radak: No. Eliyahu was sustained by the food in his innards; it was not [fully] digested or expelled for 40 days. Regarding Moshe, it does not say "due to the eating."
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2.
Malbim: Yes. After 40 days on Sinai without eating, Moshe merited a revelation of Kevod Hashem below and rays (radiance) of glory. Eliyahu, through a spiritual food, his body was purified for 40 days until he came to Har ha'Elokim and saw a great vision.
R. Bechayei, Moshav Zekenim (Shemos 24:16): Moshe was in the cloud for six days before Hashem called him to ascend, in order to empty all food out of his innards.
