Numbers 12 Three Is Not the Only Place Scholars Point to for Evidence of Mosaic Authorship

There are a couple of incidents in numbers that scholars point to as more evidence of tora having been edited over a long period of time, centuries. The word poisonous is the hebrew word seraphim, and is a plural noun from the root that typically means burning. In numbers 21, they are clearly serpents that act in a seraphimish way, and they bite, and that bite leads to death. They're poisoned and they die. That seems like a warranted translation.