The Nephilim were on the earth in those days(and also after this) when the sons of God would sleep with the daughters of humankind, who gave birth to their children. They were the mighty heroes of old, the famous men.
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TSK · Numbers 16:2
Treasury of Scripture Knowledge references in NET.
Genesis 6:4
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Numbers 12:1
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Miriam and Aaron Oppose Moses Then Miriam and Aaron spoke against Moses because of the Cushite woman he had married(for he had married an Ethiopian woman).
Numbers 27:3
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“Our father died in the wilderness, although he was not part of the company of those that gathered themselves together against the LORD in the company of Korah, but he died for his own sin, and he had no sons.
From Ephraim there were 20,800 warriors, who had brought fame to their families.
Ezekiel 23:10
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They exposed her nakedness, seized her sons and daughters, and killed her with the sword. She became notorious among women, and they executed judgments against her.