פירוש על במדבר 21:8

על נס means [SET IT] UPON A POLE which is termed perche in O. F. Similar is, (Isaiah 30:17) “And like a polo (banner) upon the hill”; (Isaiah 49:22) “I will lift up my pole (banner)”; (Isaiah 13:3) “Lift up a banner." Because it is lofty so that it can serve as a sign and as evidence of something it is called נס, something raised on high (cf. Rashi on Exodus 20:17).

עשה לך שרף, the snake should be constructed of material which is associated with שרפה, burning. The association with “burning one’s tongue” should be uppermost in their minds when contemplating their sin which had been that they allowed their tongues to utter thoughts that angered G’d. They would repent when looking at a snake called שרף, something which “burns” (transitively).

עשה לך שרף, "make a fiery snake for yourself, etc." Our sages in Avodah Zarah 44 have this to say on the peculiar word לך, for yourself, in our verse. "The Torah says לך to tell us that Moses was to construct the serpent using his own funds. The reason for this was that a person may not forbid the use of something which is not his." Thus far the Talmud. The meaning of these words is that seeing Moses had made the serpent using his own funds it became his personal property. No one has the right to forbid others something that is not his. [The problem was that in the days of King Chiskiya (Kings II chapter 18) the people appear to have offered incense to this copper snake Moses had made, and to prevent them from doing so King Chiskiyah broke this snake into little pieces. Ed.] Seeing Moses had made this copper snake, the leaders of subsequent generations had been unable to destroy this snake or to forbid the people to worship it in some form. This explanation of the words עשה לך is one that emerged in the course of historical developments. At this time it is hardly likely that G'd meant for Moses to pay for the snake out of his own funds in order that at a later time the kings or religious leaders should be unable to forbid the people to use it as an object of worship. We must understand why G'd would have phrased His instructions so that we could have understood them to mean that Moses pay for the snake. We must also try and understand why G'd called it a שרף, whereas what Moses made is described as נחש (verse 9). Furthermore, we must try and understand why G'd decreed that an object such as this, which resembled a form of idol, had to be made altogether and why looking up to it would heal a person who had sustained a bite. Our sages in Rosh Hashanah 29 claim that as long as the Israelites looked heavenwards this was a demonstration of their faith in G'd, etc. If indeed this was all that G'd had in mind, why did He not order them to look straight at heaven instead of looking at the snake as an intermediary?