Albert Barnes Commentary Lamentations 4:15

"Depart ye, they cried unto them, Unclean! depart, depart, touch not! When they fled away and wandered, men said among the nations, They shall no more sojourn [here]." — Lamentations 4:15 (ASV)

Men cried to these priests, “Away! Unclean! Away! Away! Touch not.” “Unclean” was the cry of the leper whenever he appeared in public: here it is the warning shout of those who meet the murderers.

When they fled away and wandered - These priests fled away from the city, but with uncertain steps, not knowing where to find refuge. They find themselves abhorred abroad as well as at home.

It is quite possible that this verse records a real occurrence, if not during the siege, in any case during the last years of Zedekiah’s reign.