This Hebrew word, in its plural form, is translated “seraphs” in Isaiah 6:2, 6 and means “fiery” or “burning.” It is often used to modify the general Hebrew term for serpent (na·hhashʹ) and may then be translated as “poisonous,” perhaps as referring to the burning and inflaming effect of the venom. (Deut. 8:15) It is first mentioned at the time of God’s inflicting punishment on the rebellious Israelites by sending “poisonous serpents [nehha·shimʹ sera·phimʹ]” among them. After Moses’ intercession, Jehovah instructed him to make a “fiery snake,” to be placed on a signal pole to which those bitten could then look and be healed and live. Moses formed the snake of copper. (Num. 21:6-9; 1 Cor. 10:9) Jesus gave prophetic significance to this by stating: “Just as Moses lifted up the serpent in the wilderness, so the Son of man must be lifted up, that everyone believing in him may have everlasting life.”—John 3:14, 15.
At Isaiah 14:29 and 30:6 a “flying fiery snake” is mentioned in God’s judgment against Philistia and in description of the wilderness area to the S of Judah. The expression “flying” is considered by some to refer to the rapid darting or lightninglike striking through the air done by venomous snakes when attacking.