Direct translation, "The good can be the teacher to the bad; the bad is the good's asset" By meaning, "The bad can learn from the good while the bad is a reminder to the good [not to deviate from righteousness]"

善人可以做为恶人们的老师，不善的人也可以作为善人的借鉴. The morally just can be teachers to the unjust, and the morally unjust can be like mirrors (or a standard to measure oneself against) for the just.

1.At first,we should define what is "善人” and "不善人“. A person who has good personal qualities could be "善人“；on the contrary is "不善人”. (So in this situation, "善人“means a person who is kind or nice.) Or a person who is the authority in a field; on the contrary is "不善人”（In this condition, "善人”means a person who is very good at doing something.) There are two kinds of definition on internet about "善人“;but in my opinion, both of them are make sense. 2."师“ means: teacher, standard, example, imitator 3."资” means: reference material Apparently, this sentence means" Good people could be the teacher of bad people, and bad people could provide reference material to good people." Extended meaning: " Good people could show bad people what is good, and bad people could correct themselves from what they learn or see on good people; Bad people would show to good people which is bad, so good people could warn themselves do not do that or avoid doing that." Of course, we can not just say "good" people and "bad" people in this condition, actually there is no absolute "good" or "bad" person in the world. But i don't know how to express them accurately.

"善人"means someone of good quality ,this kind of people can be the teacher of those bad guys;and the latter's bad manners can be the mirror of the former to check themselves.My English is not good......

This is Japanese writing. 善人の者は不善人の師。不善人の者は善人の資。 ぜんにん の もの は ふぜんにん の し。ふぜんにん の もの は ぜんにん の し。 As for English translation, it seems there are already good explanations by friends here.