Charles Ellicott Commentary Numbers 21:8

"And Jehovah said unto Moses, Make thee a fiery serpent, and set it upon a standard: and it shall come to pass, that every one that is bitten, when he seeth it, shall live." — Numbers 21:8 (ASV)

Make you a fiery serpent.— The single Hebrew word which is here employed is saraph (a seraph), or burning one, as in Numbers 21:6, where the word nehashim — serpents — occurs also. The meaning is explained in the following verse, in which it is said that Moses made a serpent of brass.

Set it upon a pole.— Better, a standard. The Septuagint have σημεῖον, the Vulgate signum. The Hebrew word (nes) is the same which occurs in Exodus 17:15, Jehovah-nissi—i.e., Jehovah is my standard or banner.