The origin of the concept of angels goes back further than the Bible, to the days of primitive religion. In that regard, the Encyclopaedia Britannica classifies angels and demons together, with "various spiritual beings, powers, and principles that mediate between the realm of the sacred or holy--i.e., the transcendent realm--and the profane realm of time, space, and cause and effect" (Fredericksen). Customarily, in Western culture the angels are "benevolent," and the demons are "wicked," though it appears that in Asian and African cultures the same spirit may sometimes be good and sometimes evil. The overriding point about the origin of angels as mediators, however, is that they function as a liaison between human experience and the experience, or power, of the divine and/or eternal. They are, in short, a kind of buffer between man and God.
Angels are a continual presence in both the Old and New Testaments. At Genesis 16.7-11, an angel of the lord appears to Hagar to explain that she will have a son called Ishmael, although at Gen. 17.16-17, it is God himself who tells Abraham that his wife Sarah will also have a son. At Gen. 18, Abraham interacts with the angels who have come to destroy the cities of the plain, pleading with them not to destroy Sodom if he can find enough just men there to save it. In Gen. 19, Lot plays host to and protector of two angels when the wicked men of Sodom besiege his household in order to (carnally) "know" them (Gen. 19.5). In these passages, the angels are bearing God's message and are preparing to report back to the situation on the ground in a way that seems meant to seal God's decision. They are also agents of God's providence, inasmuch as they warn Lot to take his family out of the plain and not to look back on the planned destruction of the cities there (Gen. 19.17).
The mediating agency of angels is illustrated at Gen. 21.17-20, after Sarah forces Abraham to cast Hagar and Ishmael out into th...