May God grant you the grace of good company! A very important need of the disciple is to associate with these people. Such association makes a deep impression. It is a total attack on a person’s temperament and habits, to such an extent that a falcon, by associating with men, becomes wise, and a parrot learns to speak, while a horse, because it associates with men in its training, loses its animal traits and takes on those of men! […] Association overcomes not only innate habits but also one’s created temperament. […]
The Prophet (s.a.w.s) is reported to have said: “A man chooses the religion and path of his friend. Take note of who his associates are!” If his companions are good, then he himself, even though he is bad, will become good, because their magnanimity will effect a change in him. On the other hand, if he associates with bad companions, he, too, will become bad, and even though he was good, he will end up by becoming bad. […] Malik ibn Dinar once said: “Do not associate with any brother or friend if you derive no benefit therefrom for your faith or for the world to come. Such company should be considered as forbidden for you.”
The proper way of associating with others has been thus expressed: “Your associates will either be senior to you or junior to you. If you associate with your elders, you should be the one to derive some benefit from their company.
If, on the other hand, you associate with people younger than yourself, then they should profit from the contact and learn something from you that will deepen their faith. If you also learn something from then, then your faith, too, will be deepened.” […] The etiquette of associating with others is to treat everyone in a manner that befits his or her position. A person should be respectful towards elders, affable with peers, and kindly disposed towards those who are younger. He should consider elders as parents, peers as brothers and sisters, and those junior to him as his children. […]
When association becomes perfect it provides the best preconditions for mystical states. Do you not see that the most important group of all was constituted by the companions of the Prophet (s.a.w.s)? Their knowledge, grasp of judicial matters, worship, devotion, and trust in God knew no equal. Their contentment had no connection with any single thing except their association with the Prophet (s.a.w.s), which was the best of all possible states. One of the practices of this group was to avoid saying: “This is mine and that is yours! If things had been like that, this would not have happened! O that this might have happened! O that this might not have happened! If only you had done so! Why did you not do so?” All this is the way ordinary people talk.
From Sharafuddin Maneri, The Hundred Letters (New York: Paulist Press, 1980), pp. 289-292