ואל תתחבר לרשע... (אבות א:ז)
Do not associate with a wicked person...
The people with whom a person associates generally end up having a profound effect upon him. Shlomo Hamelech informs us (Mishlei 3:34), "If one associates with a scoffer, ultimately he will end up scoffing. [If one associates] with the humble, ultimately his actions will find favor in the eyes of men." Accordingly, the Tanna warns us not to associate with a wicked person.
So what is the Jew in exile, surrounded by gentiles, supposed to do? Where should he live and what vocation should he pursue? Wherever he goes and whatever job he chooses will most probably bring him in contact with less than pious individuals similar to those mentioned by the Tanna.
The answer can be found in the Torah. Forced to flee from his brother Eisav, Yaakov Avinu spends the following twenty years with his uncle Lavan. Lavan was not merely a trickster; he was downright wicked. The haggadah makes Pharoah look righteous in comparison to Lavan who endeavored to annihilate every last vestige of Judaism. Yet, Yaakov survived the ordeal without suffering from the negative influence of his employer. How did he do it?
Yaakov himself answers the question in the message he sent to Eisav: "I have sojourned with Lavan; and I observed the 613 mitzvos and did not learn from his evil ways" (Bereishis 32:5, as explained by Rashi). He emphasized the fact that although he spent twenty years in close proximity to Lavan, it was always as a sojourner, not as a settler. Lavan might have been his boss, but he never forged a relationship with him. While we live and work in close proximity with many secular people, we must ensure that we do not cultivate relationships with those who are immoral.
What could be so dangerous about a business relationship? After all, I certainly am not going to start acting in the decadent and sinful way that my associate behaves. The Bartenura cites the Medrash who compares the association with a wicked person to one who enters a tannery. Even if he leaves without taking a single item from the tannery, he will still give off a foul smell which he picked up from simply entering the building. Likewise, associating with wicked people will leave a person tainted even if he does not actually emulate their conduct.
While the Tanna referred specifically to wicked people, his instruction certainly applies to anything that is potentially wicked. Subscriptions to periodicals that contain unsuitable content, internet connections and contacts and spiritually questionable vacation spots are some examples of potentially dangerous things that can negatively influence a person. Yet, people assuage any feelings of guilt and assure themselves, "I know myself. I know how to be careful and I won't be negatively affected." Even if you are correct in your assessment and you won't change your conduct, you still wouldn't want to take the chance of ending up with a "foul smell." Instead, find someone (or something) who has the ability to positive influence you. That way, even if you don't succeed in emulating his actions, some of his "pleasant aroma" will rub off and aid you in your ascension up the spiritual ladder.