Charles Ellicott Commentary Exodus 24:18

"And Moses entered into the midst of the cloud, and went up into the mount: and Moses was in the mount forty days and forty nights." — Exodus 24:18 (ASV)

Moses was in the mount forty days and forty nights. —During the whole of this time he took no food (Deuteronomy 9:9). Compare the fast of Elijah (1 Kings 19:8), and that of our blessed Lord (Matthew 3:2). Modern imitations are in all probability impostures.