Chabad.org — English translation + Rashi
Torah Temimah: Dan is “מאסף לכל המחנות” — the rear-guard that gathers stragglers and lost objects of the other camps.
English: “The banner of the camp of the children of Dan, the gatherer for all the camps.”
Rear-guard role — Dan closes the march and recovers what was left behind.
The last camp is charged with the chesed of not abandoning the weak or the lost.