As-sallamu aleykum,
"Those who are merciful have mercy shown them by the compassionate one, if you show mercy to those who are in the earth, he who is in heaven will show mercy to you."
"Kindness is a mark of faith: an whoever hath not kindness hath not faith."
"Whoever is kind to his creatures, God is kind to him; therefore be kind to man on earth, wether good or bad; and being kind to the bad, is to withold him from badness, thus in heaven you will be treated kindly."
"What actions are most excellent? To gladden the heart of a human being, to feed the hungry, to help the afflicted, to lighten the sorrow of the sorrowful and to remove the wrongs of the injured."
Reconignse any of these sayings? This is Muhammad (saws) speaking.... Friendship is KEY because it is of LOVE and Islam is peace and Islam is LOVE........ Someone asked Muhammad(saws)What is Islam? And he replied "purity of speech and
CHARITY."
If you cannot love others, you cannot even begin to love the creator.... How can you hold grudges and hatred of all other amazing creations of Allah? Subhan Allah! You cannot.... So I would say it is a MUST to be friends with non-Muslims... To be a true Muslim....
That then is God your Lord;
there is
no god but He,
the
Creator of everything.
So serve Him,
for
He is Guardian over everything.
The eyes attain Him not, but He attains the eyes;
He is the All-subtle, the All-aware. (6:102-103)
Think about it.