Why did Moshe call Dasan and Aviram?
Rashi: He called them to him in order to appease them. 1
Ramban: He called them to warn them and their cohorts and to appease them. 2
Targum Yonasan and Rashbam: Moshe sent messengers to call them to a Din Torah.
Why did Moshe not call On ben Peles?
Ramban: After the initial stage of rebellion, On went home. Moshe did not call him because he was subordinate to Dasan and Aviram, and he figured that if they would relent, so would he. 1
What are the implications of "Lo Na'aleh"?
Rashi: By implication, they predicted that they would go down to below the ground. 1