Fallen angels are angels who were expelled from heaven. The literal term "fallen angel" does not appear in any Abrahamic religious texts, but is used to describe angels cast out of heaven or angels who sinned. Such angels often tempt humans to sin.
The idea of fallen angels derived from the Book of Enoch, a Jewish pseudepigraph, or the assumption that the "sons of God" (בני האלוהים) mentioned in Genesis 6:1–4 are angels. In the period immediately preceding the composition of the New Testament, some sects of Judaism, as well as many Christian Church Fathers, identified these same "sons of God" as fallen angels. During the late Second Temple period the biblical giants were sometimes considered the monstrous offspring of fallen angels and human women. In such accounts, God sends the Great Deluge to purge the world of these creatures; their bodies are destroyed, yet their peculiar souls survive, thereafter roaming the earth as demons. Rabbinic Judaism and Christian authorities after the third century rejected the Enochian writings and the notion of an illicit union between angels and women producing giants. Christian theology indicates the sins of fallen angels occur before the beginning of human history. Accordingly, fallen angels became identified with those led by Lucifer in rebellion against God, also equated with demons.
In the Books of Enoch, the first Book of Enoch devotes much of its attention to the fall of the watchers. The Second Book of Enoch addresses the watchers (Gk. egrḗgoroi) who are in fifth heaven where the fall took place. The Third Book of Enoch gives attention to the unfallen watchers.
The use of the term "watchers" is common in the Book of Enoch. The Book of the Watchers (1 Enoch 6–36) occurs in the Aramaic fragments with the phrase irin we-qadishin, "Watchers and Holy Ones", a reference to Aramaic Daniel. The Aramaic irin "watchers" is rendered as "angel" (Greek angelos, Coptic malah) in the Greek and Ethiopian translations, although the usual Aramaic term for angel malakha does not occur in Aramaic Enoch.
The Nephilim (/ˈnɛfɪˌlɪm/; Hebrew: נְפִילִים Nəfīlīm) are mysterious beings or people in the Hebrew Bible who are described as being large and strong. The word Nephilim is loosely translated as giants in most translations of the Hebrew Bible, but left untranslated in others. Some Jewish explanations interpret them as hybrid sons of fallen angels (demigods).
The main reference to them is in Genesis 6:1–4, but the passage is ambiguous and the identity of the Nephilim is disputed. According to the Book of Numbers 13 : 33, a report from ten of the Twelve Spies was given of them inhabiting Canaan at the time of the Israelite conquest of Canaan.
The Book of Enoch (also 1 Enoch;[note 1] Hebrew: סֵפֶר חֲנוֹךְ, Sēfer Ḥănōḵ; Ge'ez: መጽሐፈ ሄኖክ, Maṣḥafa Hēnok) is an ancient Hebrew apocalyptic religious text, ascribed by tradition to the patriarch Enoch who was the great-grandfather of Noah. The Book of Enoch contains unique material on the origins of demons and Nephilim, why some angels fell from heaven, an explanation of why the Genesis flood was morally necessary, and prophetic exposition of the thousand-year reign of the Messiah. Three books are traditionally attributed to Enoch, including the distinct works 2 Enoch and 3 Enoch. None of the three books are considered to be canonical scripture by the majority of Jewish or Christian church bodies.