The Shaykh – rahimahullaah – said: 
Know O pious brother – may Allaah make our affairs good – that the manners of companionship and good relationships are of various types, of which I will explain, such as will show the person of intellect the manners of the Believers and the Pious; and come to know that Allaah the Most Perfect, the Most High has made them a mercy and helpers towards each other, which is why the Messenger of Allaah sal-Allaahu ’alayhe wa sallam said,
“The example of the Believers, in their mutual love and mercy is like the example of a body, if one part feels pain, then all of the body suffers in sleeplessness and fever.” 
And he ’alayhis-salaam said,
“The Believer to the Believer is like a solid building, one part supporting the other.” 
The Prophet ’alayhis-salaam also said,
“The souls are arrayed armies, so those who knew one another before, will be friendly … ” 
So if Allaah intends good for His servants, He grants them companionship of the people of the Sunnah, righteousness and adherence to the Religion.; and keeps him free from the companionship of the people of innovations. The Prophet ’alayhis-salaam said,
“A person is upon the religion of his friend, so let every one of you look to whom he keeps as a friend.” 
‘About a person, do not ask, but ask about his companion; Since every companion follows his friends.’
From The Manners of Companionship:
Good manners with the brothers and companions, following the Messenger of Allaah sal-Allaahu ’alayhe wa sallam as he said, when it was said to him, What is the best of what a person is given? So he replied,
Making One’s Opinion Good:
From the manners of companionship is behaving well regarding the faults that he sees of his companions, since Ibn Maazin said, “The Believer seeks excuses for his brothers, whilst the hypocrite seeks out their faults.”
And Hamdoon al-Qassaar said, “If one of your brothers commits an error, then seek ninety excuses for him, and if not, then you are the blameworthy one.”
Companionship with the Believers:
To keep companionship with one whose Religion you trust and who is trustworthy, both inwardly and outwardly. Allaah – the Most High – says,
“You will not find anyone who believes in Allaah and the Last Day, making friendship with those who oppose Allaah and His Messenger, even though they were their fathers, sons, brothers or their relatives. For such He has written eemaan (faith) in their hearts, and strengthened them with a spirit (proofs, light and guidance) from Himself. And We will admit them into gardens underneath which rivers flow, to dwell therein forever. Allaah is pleased with them, and they are pleased with Him. They are the Party of Allaah, indeed it is the Party of Allaah that will be successful.” [Sooratul-Mujaadilah (58):22]
Forms of Companionship
For the Shaykhs and elders: with respect to service and to carry out their needs.
For those of the same peer group and those of the ‘middle rank’: with sincere advice, giving what you have and being prepared to carry out their wishes.
For the students and younger ones: by guidance, teaching of manners, carrying out what knowledge demands, guidance to the manners of the Sunnah, rulings concerning the matters of the heart, and to guide them to develop good manners.
From the manners of companionship is overlooking mistakes of the brothers and not reprimanding them. So al-Fudayl Ibn ’Iyaad (d.187H) said, “Chivalry is to overlook the mistakes of the brothers.”
Ibnul-A’raabee (d.231H) said, “Forgetting the harms caused by the brothers, causes your love of them to persist.”
So it is binding upon the Believer, that he avoids seekers of this world, since they will bring him down to the level of seeking it, and this will distance him from his salvation and it will distance him from remaining alert and being aware of it. Rather, he must strive hard in attaining the companionship of the good and the seekers of the Hereafter.
Therefore, Dhun-Noon (d.245H) said to the one whom he advised, “Accompany the one whom you will be safe from outwardly, and whom – when you see him – it helps you in doing good and reminds you of your Lord.”
Agreement with the Brothers
And from them is: not to differ much with the brothers, but continue agreeing with the brothers in those things allowed by knowledge and the Sharee’ah.
Aboo ’Uthmaan said, “Agreeing with the brothers is better than showing compassion for them.”
Leaving of Envy
That he does not envy the signs of Allaah’s bounty upon them. Rather, he should be happy for that and praise Allaah for it, just as he would praise Allaah if it were seen upon him. Allaah – the Most High – censures the envious one:
“Or do they envy men for what Allaah has given them from His bounty.” [Sooratun-Nisaa’ (4):94]
The Prophet sal-Allaahu ’alayhe wa sallam said, “Do not envy one another.” 
To Keep a Feeling of Modesty
That he has hayaa’ (modesty and shame) at all times, as he – ’alayhis-salaam – said, “Eemaan (faith) has sixty or seventy odd branches, the most excellent of them is witnessing that none has the right to be worshipped besides Allaah, and the lowest branch is removing something harmful from the road, and hayaa’ is from eemaan.” 
He – ’alayhis-salaam – also said, “Hayaa’ is from eemaan, and eemaan is from Paradise. Speaking obscenely is from coarseness and coarseness is from the Fire.” 
Companionship of the Dignified
To accompany the one who he has a feeling of respect for, so that this prevents from acting contrary to the Sharee’ah. ’Alee radi-Allaahu ‘anhu said, “Enliven your feeling of hayaa’ (shame), by sitting before those whom you feel shame.”
Ahmad Ibn Hanbal (d.241H) – rahimahullaah – said, “I have not been led into calamity except by accompanying those before whom I do not feel shame.”
To have cheerfulness of the face, kindness of the tongue, largeness of the heart, outspreading the hands, withholding anger, leaving off pride, keeping people’s honour in mind and showing happiness at their companionship and brotherhood.
Companionship of the Wise Scholar
From good companionship is that he does not accompany except a Scholar, of a person who is mild, intelligent and has knowledge.
Dhun-Noon – rahimahullaah – said, “Allaah has not disrobed any one of His servants or a robe better than intellect, and has not adorned him with a necklace better than knowledge, nor adorned him with anything better than mildness. And the completeness of that is taqwaa (fear of Allaah).”
Giving Sincere Advice
Having a clean heart with regards to the brothers and advising them, as Allaah – the Most High – said:
“Except he who comes to Allaah with a clean heart.” [Sooratush-Shu’araa (26):89]
Saree as-Saqatee (d.257H) – rahimahullaah – said, “One of the best manners of righteousness is having a good heart as regards the brothers and to give them sincere advice.”
Not Breaking Promises
Since this is from hypocrisy, and he – ’alayhis-salaatu was-salaam – said, “The signs of the hypocrite are three: When he speaks he lies, when he makes a promise he breaks it and when he is entrusted he acts deceptively.” 
Sufyaan ath-Thawree (d.164H) – rahimahullaah – said, “Do not make a promise to your brother and then break it, so that love turns to hate.”
Manners of Companionship, Book by Shaykh Badrud-Deen al-Ghazzee 
Footnotes He is the muftee and faqeeh, Abul-Barakaat Badrud-Deen al-Ghazzee. For his biography, refer to Shadharaatudh-Dhahab (8/403-406) of Ibnul-’Imaad and al-A’laam (7/59) of az-Ziriklee.  From Aadaabul-’Ishrah wa Dhikrus-Suhbah wal-Ukhuwwah (p. 9-20) with the checking and authentication of hadeeth based upon that of Shaykh ’Alee Hasan al-Halabee and also Shaykh Mashhoor Hasan Salmaan.  Related by al-Bukhaaree (no. 6011) and Muslim (no. 2586), from an-Nu’maan Ibn Basheer radi-Allaahu ‘anhu.  Related by al-Bukhaaree (no. 481) and Muslim (no. 2585), from Aboo Moosaa al-Ash’aree radi-Allaahu ‘anhu.  Saheeh: Related by al-Bukhaaree (6/369) with ta’leeq (suspension), from ’Aa‘ishah radi-Allaahu ‘anhaa. It was connected by Aboo Ya’laa in al-Musnad (no. 4381) with an isnaad whose narrators are from as-Saheeh – as occurs in al-Majma’ (8/88) of al-Haythamee.  Hasan: Related by Ahmad (2/303), Aboo Daawood (no. 4812) and at-Tirmidhee (no. 2484), from Aboo Hurayrah radi-Allaahu ‘anhu. It was authenticated by Imaam an-Nawawee in Riyaadus-Saaliheen (no. 174).  Saheeh: Related by Wakee’ in az-Zuhd (no. 423), Ibn Hibbaan (1/427) and at-Tabaraanee in al-Kabeer (1/147), from Usaamah Ibn Shareek radi-Allaahu ‘anhu. It was authenticated by al-Haafidh al-’Iraaqee in Takhreejul-Ihyaa‘ (2/157).  Related by al-Bukhaaree (10/484) and Muslim (no. 2564), from Aboo Hurayrah radiyallaahu ’anhu.  Related by al-Bukhaaree (1/44) and Muslim (1/46).  Saheeh: Related by Ahmad (2/501) and at-Tirmidhee (no. 2077) with a saheeh isnaad, from Aboo Hurayrah radi-Allaahu ‘anhu.  Related by al-Bukhaaree (5/289) and Muslim (1/76). Taken from Aadaabul-’Ishrah wa Dhikrus-Suhbah wal-Ukhuwwah (p. 9-20)