1)
Who came to bring the Aron?
1.
Malbim: Everyone [in the city], for its honor.
2)
What is the meaning of "Kidshu"?
1.
Rashi citing Targum Yonasan: They prepared [him].
2.
Malbim: They separated [him] from all other involvements.
3)
What will he do to guard the Aron?
1.
Radak: He will guard the house (in which the Aron will be) in Taharah, and sweep and wet the floor (to settle dust) in front of it.