Friendship is nil unless its limits are kept. He who does not keep these limits should not be regarded as friend. The first limit is that the inner self and the appearance should be identical. The second limit is that the friend should regard your goodness as his goodness and your evil as his evil. The third limit of friendship is that a position or fortunes should not change the friend’s relation with his friends. The fourth limit is that the friend should not deprive his friend of anything that he is capable of doing. The fifth limit which is the most comprehensive is that the friend should never leave his friend alone in calamities.
Imam Al-Sadiq (as)