Moses, arose and went to Dathan and Aviram, the elders of Israel followed him.
Bemidbar 16:25
Dathan and Aviram had openly demonstrated their animosity toward Moses, charging him with being a despot and an impostor. Moreover, G-d Himself had already sealed their punishment, instructing Moses to save only the others from their impending fate. Still, Moses did not give up hope that his "enemies" would repent, doing everything in his power to influence them to reconsider.
We must learn from Moses to always do whatever we can to bring our brethren back to G-d and the Torah -- even when it seems that all hope is lost. This is true even when they are ignoring their faith intentionally, and all the more so when they are acting out of ignorance.
--Kehot's Chumash
Bemidbar
Synagogue Edition