What are the implications of the phrase "Hirgu Ish Anashav!"?
Ramban #2: It implies that the Beis-Din (Sanhedrin, consisting of twenty-three Dayanim) of each tribe was to kill the sinners of their tribe and the thousand over which they were appointed. 3
Ramban #4: Hashem in his mercy, told Moshe to instruct the Dayanim to sentence the sinners to death, in order to stop the plague that was killing the innocent and the guilty alike. However when Pinchas sprang into action, 'Davened and stopped the plague,' 5 causing Hashem's anger to abate, the plague stopped and there was no longer any need for Beis-Din to carry out the death-sentence. 6
Rashi: Of whom there were eighty-six thousand.
Ramban: Which means that a hundred and fifty-seven thousand two hundred people (over a quarter of the nation) died, and that they had increased considerably between the previous census (in Bamidbar) and the next one (in Pinchas).