(Translations according to New International Version. Note that translations frequently differ. In the King James Version of the Bible, "Nephilim" is translated as "giants" in the following examples.)

The term "Nephilim" occurs just twice in the Hebrew Bible, both in the Torah. The first is Genesis 6:1-4, immediately before the Noah's ark story:

1. When men began to increase in number on the earth and daughters were born to them,
2. the sons of God saw that the daughters of men were beautiful, and they married any of them they chose.
3. Then the LORD said, "My Spirit will not contend with man forever, for he is mortal; his days will be a hundred and twenty years."
4. The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of men and had children by them. They were the heroes of old, men of renown.
The second is Numbers 13:32-33, where the Hebrew spies report that they have seen fearsome giants in Canaan:

32. And they spread among the Israelites a bad report about the land they had explored. They said, "The land we explored devours those living in it. All the people we saw there are of great size.
33. We saw the Nephilim there (the descendants of Anak come from the Nephilim). We seemed like grasshoppers in our own eyes, and we looked the same to them."
Piano Improvisation by David Hart