Exodus 24:18
16 The glory of the Lord resided on Mount Sinai, and the cloud covered it for six days. On the seventh day he called to Moses from within the cloud. 17 Now the appearance of the glory of the Lord was like a devouring fire on the top of the mountain in plain view of the people. 18 Moses went into the cloud when he went up the mountain, and Moses was on the mountain 40 days and 40 nights.
Numbers 13:25
23 When they came to the valley of Eshcol, they cut down from there a branch with one cluster of grapes, and they carried it on a staff between two men, as well as some of the pomegranates and the figs. 24 That place was called the Eshcol Valley, because of the cluster of grapes that the Israelites cut from there. 25 They returned from investigating the land after 40 days. 26 They came back to Moses and Aaron and to the whole community of the Israelites in the wilderness of Paran at Kadesh. They reported to the whole community and showed the fruit of the land. 27 They told Moses, “We went to the land where you sent us. It is indeed flowing with milk and honey, and this is its fruit.
Notes and References
"... The number forty is significant in the Bible: the rains of the Flood in Genesis occurred for forty days and forty nights (Genesis 7:4, 12); Moses met twice with the Lord on the mountain for forty days and forty nights (Exodus 24:18; 34:28; Deuteronomy 9:9, 11, 18, 25, 10:10); the spies of Israel spent forty days spying out the land of Canaan (Numbers 13:25); Israel spent forty years in the wilderness until they came to the land of Canaan (Exodus 16:35; Deuteronomy 2:7; 8:2, 4; 29:5; Nehemiah 9:21; Psalm 95:10; Amos 2:10); the forty years in the wilderness served as punishment for their lack of faith in response to the spies (Numbers 14:33–34; Joshua 5:6; Psalm 95:10); Israel spent forty years under the rule of the Philistines (Judges 13:1); Elijah was provided for in his flight from Jezebel forty days and forty nights (1 Kings 19:8); Jonah prophesied that in forty days Nineveh would be overthrown (Jonah 3:4); and Ezekiel enacted a prophetic sign of Jerusalem’s downfall by laying on his side forty days, a day for each year (Ezekiel 4:6). All of these reveal an importance of the number forty in Israel’s history. (Jeremias, New Testament Theology, observes that “forty is a common symbolic number, which denotes times of oppression and of curse.”) ..."
Kennedy, Joel The Recapitulation of Israel: Use of Israel’s History in Matthew 1:1-4:11 (pp. 194-195) Mohr Siebeck, 2008