Parshas Terumah: Chizkuni - Long Poles Are Big Obstacles
"Lo Yasuru Mimenu" It is a Lav (negative commandment) to remove the poles from the Aaron. Chizkuni asks, why do we only find this prohibition by the Aaron and not by the other vessels that also had poles - Shulchan, Mizbayach HaZahav and Mizbayach HaNichoshes?
Chizkuni answers, the poles were a hindrance and a stumbling block to have around when the Mishkan was stationary. They simply took up too much room. Therefore it would be best to have them removed at the time of encampment. However, since the Aaron was in the Kodesh HaKadoshim - a place that was only accessed once a year by the Kohen Gadal; it really wasn't in anybody's way. Therefore the Torah says specifically by the poles of the Aaron - "Do not remove them".