Sheikh Saadi says that if any one associates with bad people, although their nature may not infect him, he will be supposed to follow their ways to such an extent that if he goes to a tavern to say his prayers, it will be supposed that he is going there for drinking wine.

He adds:

"When you have selected an ignorant person as your companion,
You have branded yourself with the mark of
ignorance
Do not associate with an ignorant man,
For if you are learned in such company you will
become an ass in course of time;
And if you are not learned you will become a
greater fool."