Keeping Good Company

It is vital that the correct company is kept as Shaytaan will not fail to mislead you on account of the company you keep. The Messenger (sas) said: “The example of the good and bad company is that of a musk-seller and an iron-monger. Even if you do not buy from the musk-seller the fragrance will remain with you and even if your clothers do not get burnt by being in close proximity to the iron-monger the bad smell will remain with you.” [Reported by Bukhaaree]
The Messenger (sas) also said: “Do not be a companion except to a believer”. [Reported by Abu Daawood]

And the poet spoke the truth when he said:

Choose among the people, one who will guide you
Indeed, by a friend does one guide himself
And accompanying the evil ones is blindess and a disease
It increases the sick heart in sickness
So if you are a follower of the Sunnah
Then avoid the evil companionship

So be zealous of keeping good company and remaining only with good muslims, those who fear Allaah much and strive to worship Him. If you do so, you will never be able to count the good you will acquire, and with Allaah lies all success.
[taken from 'Shaytan and His Ways in Misleading']