The Hebrew noun sa·raphʹ, in its plural form, is translated “seraphs” in Isaiah 6:2, 6 and literally means “fiery one,” or “burning one.” It is also used in conjunction with the general Hebrew term for serpent (na·chashʹ) and has been translated “poisonous,” perhaps referring to the burning and inflaming effect of the venom. (De 8:15) It is first mentioned at the time of God’s inflicting punishment on the rebellious Israelites by sending “poisonous serpents [han·necha·shimʹ has·sera·phimʹ]” among them. After Moses’ intercession, Jehovah instructed him to make “a fiery snake” and place it on a signal pole. If those bitten would look at it, they would be healed and would live. Moses formed the snake of copper. (Nu 21:6-9; 1Co 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.”—Joh 3:14, 15.
At Isaiah 14:29 and 30:6 “a flying fiery snake” is mentioned in God’s judgment against Philistia and in the 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.