Commento su Salmi 91:7

A thousand will be stationed at your side Heb. יפל, an expression of encamping, as (Gen. 25: 18): “before the face of all his brothers did he settle (נפל).”

at your side At your left a thousand demons will be stationed, and they will not approach you to harm [you].

הבדלו מתוך העדה הזאת, “Separate yourselves from this congregation, etc.!” The reference was to the congregation of Korach seeing that Moses and Aaron stood next to them at the entrance to the Tabernacle. Moses misunderstood, thinking that the expression: “this congregation” applied to the entire Jewish nation. This is why he answered G’d by saying: “shall one man sin and You will be angry at the entire assembly (people)?” Thereupon G’d explained to him immediately that the expression העדה applied only to the rebel community, i.e. העדה הזאת. This is the meaning of the words: “move away from around the tent of Korach,” an elaboration of what G’d had said previously.
Why did G’d have to give instructions for the people who did not support Korach to separate from him physically, as if He were unable to single out the sinners and kill them only, [as He had done with the firstborn in Egypt? Ed.] Do we not have a saying that when two or three people take shelter under the same talit, the two standing on the outside would die and the one standing in the center would be saved (Midrash Rabbah in connection with the dying of the first born in Egypt)? David elaborated on his phenomenon in Psalms 91,7 when he said: “a thousand may fall at your left side and ten thousand at your right, but it (disaster) shall not reach you.” In view of all this, why did G’d insist on the people distancing themselves physically from the group supporting Korach? It was in order that the contaminated air around Korach and his fellow rebels should not infect the people around him. Just as one has to flee a town in which pestilence rages in order to escape the chance of such infection through radiation of bacteria so the people had to leave the vicinity of Korach. When Lot and family were told by the angel not to stand still while running away from the city of Sodom and his wife ignored the warning she turned into a pillar of salt, i.e. the negative fallout from the sulfur in the air caught up with her (Genesis 19,26).
Another reason for the instruction that the people standing around Korach were to put space between themselves and him may have been the well known fact that when the attribute of Justice is at work it does not distinguish between the guilty and the innocent who are in its path. It was therefore necessary for the ‘innocent’ to take action to save themselves from the attribute of Justice (compare Baba Kama 60). The reason may also have been that G’d ‘honours’ the righteous, i.e. He does not release forces of destruction while the righteous are in the immediate vicinity of the wicked to be destroyed.