Jamieson, Fausset and Brown on 1 Corinthians 15:33

33. evil communications corrupt good manners--a current saying, forming a verse in Menander, the comic poet, who probably took it from Euripides [Socrates, Ecclesiastical History, 3.16]. "Evil communications" refer to intercourse with those who deny the resurrection. Their notion seems to have been that the resurrection is merely spiritual, that sin has its seat solely in the body, and will be left behind when the soul leaves it, if, indeed, the soul survive death at all.

good--not only good-natured, but pliant. Intimacy with the profligate society around was apt to corrupt the principles of the Corinthians.