A Seraph (Hebrew שָׂרָף saraph "majestic beings with 6 wings, human hands or voices in attendance upon God, serpent, fiery serpent, poisonous serpent," from שָׂרַף saraph "to burn," plural שׂרפים Seraphim) is one of a class of celestial beings mentioned once in the Old Testament (Tanakh), in Isaiah.
Later Jewish imagery perceived them as having human form, and in that way they passed into the ranks of Angels.
In the Christian Angelic hierarchy, Seraphim represent the highest known rank of Angels.
Seraphim, literally "burning ones", is the plural of "seraph", more properly sarap. The word sarap/seraphim appears three times in the Torah (Numbers 21:6-8; Deuteronomy 8:15) and four times in the Book of Isaiah (6:2-6, 14:29, 30:6). In Numbers and Deuteronomy the "seraphim" are serpents – the association of serpents as "burning ones" is possibly due to the burning sensation of the poison. Isaiah also uses the word in close association with words to describes snakes (נחש nachash , the generic word for snakes, in 14:29, and אפעה 'eph`eh, viper, in 30:6).
Isaiah's vision of seraphim in the First Temple in Jerusalem is the sole instance in the Hebrew Bible of the word being used to describe celestial beings: there the winged "seraphim" attend God and have human attributes:
1 In the year that King Uzziah died I saw the Lord sitting upon a throne, high and lifted up; and the train of his robe filled the temple. 2 Above him stood the seraphim. Each had six wings: with two he covered his face, and with two he covered his feet, and with two he flew. 3 And one called to another and said:
"Holy, holy, holy is the LORD of hosts; the whole earth is full of his glory!""(Isaiah 6:1–3 ESV)
In Isaiah's vision the seraphim cry continually to each other, "Holy, holy, holy, is YHWH of hosts: the whole earth is full of His glory" (verses 2-3) before carrying out an act of purification for the prophet (verses 6-7). It is possible that these are winged snake-beings, but given that the word "seraphim" is not attached as an adjective or modifier to other snake-words ("nahash," etc.), as is the case in every other occurrence of the word, it is more probable that they are variants of the "fiery" lesser deities making up God's divine court.