Nameemah (Back Biting to Destroy Relations) from a Kafir (Non-Muslim)
Question

                I am a new convert to Islam, and I have a Christian brother who lives with me.

My brother does not like a person, who used to be a friend, that helped me to become a Muslim, and my brother told me some bad things about that friend.

So I had a big fight with this friend and we don't talk any more. Did I do wrong?

By the way, this friend used to ask me where I go and he used to call me a lot.

Do you think it is wrong to cut my relationship with this friend? P.S. I know that this friend likes me very much...And I think he is a good Muslim.
Praise be to Allah.Subhan Allah (Glory be to 
    Allah)! How did you cut off your ties with your Muslim brother because of 
    some news about him that was brought by a non-Muslim?
Allah says (interpretation 
    of the meaning):
“O you who believe! If a 
    rebellious evil person comes to you with news verify it…” [49:6].
This person is not just a 
    “rebellious, evil person” (fasiq), he is also a kafir (non-Muslim), so how 
    could you believe what he said and on that basis cut off ties with your 
    Muslim brother? Indeed, what you have done is wrong, and you must go back to 
    this Muslim friend, because it is not permissible for a Muslim to forsake 
    his brother for more than three days. Since he likes you and was the reason 
    why you became Muslim, you owe him a great deal. How can you cut him off? Go 
    back to him and do not leave him unless there is some clear evidence and 
    proof that you should forsake him for some serious matter that goes against 
    Islam. 
We ask Allah to grant us 
    and you guidance and strength.