The Messenger Muhammad (saw) said:
“A person is on the Deen of his friends, so let each one of you look at whom he befriends.”
From this Hadith it is clear that whomever a Muslim befriends will have impact on the way they practice Islam. Without doubt, the friends will have influence over our character and actions. For example, if Muslims surround themselves with people that are good practicing Muslims then they themselves will be motivated to good. But if Muslims are surrounded by corrupted, sinful people then they too will be affected and become corrupted. The good or bad friends and the peer pressure they can have will affect us in different ways as the Messenger explained:
“The likeness of a righteous friend and an evil friend is the likeness of a (musk) perfume seller and a blacksmith. As for the perfume seller, he may either bestow something on you, or you may purchase something from him, or you may benefit from his sweet smell. And as for the blacksmith, he may either burn your clothes, or you may be exposed to his awful smell.” (Muslim and Bukhari)
We are warned countless times from Islam to be careful of the company we keep. Always being cautious of who we befriend from the Muslims. And never can they befriend anyone who is a non-Muslim as it will have severe consequences. Hence, it is not allowed (except if we call them to Islam), as Allah mentions:
“O you who believe. Take not as your (friends, helpers, advisors..) those outside your religion (e.g. The Jews, Christians and Mushriks) since they will not fail to do their best to corrupt you. They desire to harm you severely.” (3:118)
So each of us should look to who we have as our friends as these are the people that will either aid us to reach Jannah (paradise) by encouraging us to do good and stay away from bad deeds. Or lead us to an evil destination (hell-fire) by making us neglectful of Islam and persuading us to do sin.