The rotten Apple spoils his Companion - Need help with proverb

Does anybody know what "The rotten Apple spoils his Companion" means?

Please answer as soon as you can.

It's due today!

well a rotten tomato spoils the other fresh tomatoes, same with other fruits... meaning if a person in a group is rotten, it can spoil other people too

If you hang out with someone who is shady or not nice, people will think you are like that too. Guilty by association.

:)

Or, you could take it as meaning that hanging out with people with bad qualities actually does cause you to take on those qualities yourself, which is slightly different than Kevin's interpretation (which is also valid, btw).