Allah, The Most High, said:

لَّا يُحِبُّ ٱللَّهُ ٱلْجَهْرَ بِٱلسُّوٓءِ مِنَ ٱلْقَوْلِ إِلَّا مَن ظُلِمَ وَكَانَ ٱللَّهُ سَمِيعًا عَلِيمًا

Allah does not like that the evil should be uttered in public except by him who has been wronged. And Allah is Ever All-Hearer, All-Knower. [An-Nisaa 148]

Imam As-Sadi, may Allah have mercy upon him, said:

يخبر تعالى أنه لا يحب الجهر بالسوء من القول، أي: يبغض ذلك ويمقته ويعاقب عليه، ويشمل ذلك جميع الأقوال السيئة التي تسوء وتحزن، كالشتم والقذف والسب ونحو ذلك فإن ذلك كله من المنهي عنه الذي يبغضه الله. ويدل مفهومها أنه يحب الحسن من القول كالذكر والكلام الطيب اللين. وقوله: { إِلَّا مَن ظُلِمَ } أي: فإنه يجوز له أن يدعو على من ظلمه ويتشكى منه، ويجهر بالسوء لمن جهر له به، من غير أن يكذب عليه ولا يزيد على مظلمته، ولا يتعدى بشتمه غير ظالمه، ومع ذلك فعفوه وعـدم مقابلته أولى، كما قـال تعالى: { فَمَنْ عَفَا وَأَصْلَحَ فَأَجْرُهُ عَلَى اللَّهِ } { وَكَانَ اللَّهُ سَمِيعًا عَلِيمًا } ولما كانت الآية قد اشتملت على الكلام السيئ والحسن والمباح، أخبر تعالى أنه { سميع } فيسمع أقوالكم، فاحذروا أن تتكلموا بما يغضب ربكم فيعاقبكم على ذلك. وفيه أيضا ترغيب على القول الحسن. { عَلِيمٌ } بنياتكم ومصدر أقوالكم.

Allah, The Most High, informs (us) that indeed He does not love that evil speech is uttered in public, meaning He hates that, abhors it, and punishes due to it. And this includes all evil speech that causes hurt and sadness, such as insults, false accusations, revilement, and what is similar, for indeed, all of this is from the prohibited things that Allah hates. Its (further) understanding is that indeed He loves good speech, such as Dhikr, good, gentle speech.

As for His statement, “except by one who has been wronged”, for indeed, it is permissible for him to supplicate against the one who wronged him, complain about the injustice, and openly mention the evil of the one who openly spoke ill of him, without lying about him – neither exceeding the limits of his oppression nor transgressing the limits through his insult against other than the one who oppressed him. However, pardoning and refraining from retaliation are better, as Allah said:

مَنْ عَفَا وَأَصْلَحَ فَأَجْرُهُ عَلَى اللَّه

“Whoever forgives and makes reconciliation, his reward is with Allah.” [1]

Al-Allamah Muqbil Bin Haadee al-Waadi’ee, may Allah have mercy upon him, said:

All praise belongs to Allaah, we mention the noble ‘Ulamaa with good, we direct people to them the likes of Shaykh Badee’ ad-Deen al-Bakistaanee as-Sindee, Shaykh al-Albaanee…Shaykh Rabee’ and Ibn Baaz. Our books are full of advising people to sit with those scholars and to benefit from them and their books. As for if you intend (by your question) that there is nothing with us except Tajreeh (refutation) for the people of innovation, then that is correct since they are the ones who initiate it:

لَّا يُحِبُّ ٱللَّهُ ٱلْجَهْرَ بِٱلسُّوٓءِ مِنَ ٱلْقَوْلِ إِلَّا مَن ظُلِمَ وَكَانَ ٱللَّهُ سَمِيعًا عَلِيمًا

 Allah does not like that the evil should be uttered in public except by him who has been wronged. And Allah is Ever All-Hearer, All-Knower.  [Surah an-Nisaa: 148]

So they are the ones who initiate (the revilement) and make people flee from us. So at times they say (about us that we are) ‘people of Takfeer (ejecting people from Islaam).’ And other times they say we are ‘Mutashaddidoon’ (harsh), and they say that we do not know anything from the current affairs. And on occasions they say (about us that) we only know ‘Hadathana wa Akhbarana’ (he narrated to us and he informed us – i.e. knowledge of Hadeeth). And the Prophet (ﷺ) said:  “When two people revile/insult one another, (the sin of) what they say is upon the first one (i.e. the one who initiated it), so long as the wronged one does not transgress.” [Saheeh Muslim (no.2587]

So we are defenders of the Sunnah, not (defenders of) our own selves. We hear people reviling and insulting us but we do not reply to them. The people of Sa’dah authored: ‘The Decisive Speech In Refuting The Slanderer and Liar’ – they are talking about me but I did not reply to them… And we did not refute them – all praise be to Allaah – until the people of Sa’dah died. We have no time to defend ourselves, rather, we defend the Sunnah even if it is by biting with our molar teeth. We will never let anyone speak ill of the Sunnah of the Messenger (ﷺ), whether he is a Shi’ite, a Soofee or from the Muslim Brotherhood. We sacrifice ourselves and our honour for the Sunnah.” Source: [Fadaa’ih wa Nasaa’eh, p.153-155, Shaykh Muqbil b. Haadee al-Waadi’ee, Daar al-Haramain, First Edition, 1419H/1999CE] [Translated by Ustadh Abu Abdillah Bilal Al-Kashmiri – may Allah preserve him]

Shaikh Al-Islam Ibn Taymiyyah, may Allah have mercy upon him, said:

ﻭﻟﻴﺲ ﻟﻠﻤﻌﻠﻤﻴﻦ ﺃﻥ ﻳﺤﺰﺑﻮﺍ ﺍﻟﻨﺎﺱ

ﻭﻳﻔﻌﻠﻮﺍ ﻣﺎ ﻳﻠﻘﻲ ﺑﻴﻨﻬﻢ ﺍﻟﻌﺪﺍﻭﺓ ﻭﺍﻟﺒﻐﻀﺎﺀ،

ﺑﻞ ﻳﻜﻮﻧﻮﻥ ﻣﺜﻞ ﺍﻷﺧﻮﺓ ﺍﻟﻤﺘﻌﺎﻭﻧﻴﻦ ﻋﻠﻰ

ﺍﻟﺒﺮ ﻭﺍﻟﺘﻘﻮﻱ ﻛﻤﺎ ﻗﺎﻝ ﺗﻌﺈﻟﻰ

وَتَعَاوَنُوا عَلَى الْبِرِّ وَالتَّقْوَى وَلا تَعَاوَنُوا عَلَى الإثْمِ وَالْعُدْوَانِ

وليس لأحد منهم أن يأخذ على أحد عهداً بموافقته على كل ما يريده وموالاة من يواليه ومعاداة من يعاديه،بل من فعل هذا كان من جنس جنكز خان وأمثاله الذين يجعلون من وافقهم صديقاً واليا، ومن خالفهم عدوَّا باغيا، بل عليهم وعلى أتباعهم عهد الله ورسوله بأن يطيعوا الله ورسوله ويفعلوا ما أمر الله ورسوله ويحرموا ما حرم الله ورسوله ويرعوا حقوق المعلمين كما أمر الله ورسوله، فإن كان أستاذ أحد مظلوماً نصره، وإن كان ظالماً لم يعاونه على الظلم بل يمنعه منه كما ثبت في الصحيح أنه قال:

(انصر أخاك ظالماً أو مظلوماً. قيل: يا رسول الله: أنصره مظلوماً فكيف أنصره ظالماً؟. قال تمنعه من الظلم فذلك نصرك إياه).

وإذا وقع بين معلم ومعلم أو تلميذ وتلميذ أو معلم وتلميذ خصومة ومشاجرة لم يجز لأحد أن يعين أحدهما حتى يعلم الحق، فلا يعاونه بجهل ولا بهوى، بل ينظر في الأمر، فإذا تبين له الحق أعان المحق منهما على المبطل سواء كان المحق من أصحابه أو أصحاب غيره، وسواء كان المبطل من أصحابه أو أصحاب غيره، فيكون المقصود عبادة الله وحده وطاعة رسوله واتباع الحق والقيام بالقسط

قال تعالى

يا أيها الذين آمنوا كونوا قوامين بالقسط شهداء لله ولو على أنفسكم أو الوالدين والأقربين، إن يكن غنياً أو فقيراً فالله أولى بهما، فلا تتبعوا الهوى أن تعدلوا وإن تلووا أو تعرضوا فإن الله كان بما تعملون خبيراً

It is not allowed for the teachers to initiate (illegal) partisanship between the people and do that which would cause enmity and hatred between them; but rather they should be brothers who cooperate upon righteousness and piety, as Allah, The Most High, said:

وَتَعَاوَنُوا عَلَى الْبِرِّ وَالتَّقْوَىٰ ۖ وَلَا تَعَاوَنُوا عَلَى الْإِثْمِ وَالْعُدْوَانِ

Help you one another in Al-Birr and At-Taqwa [virtue, righteousness and piety]; but do not help one another in sin and transgression.][Al-Ma’idah. 2]

It is not allowed for anyone of them to receive a pledge from anyone to be in agreement with him in everything he wants – having allegiance to the one he is allied to and enmity against the one he harbours enmity, and whoever does this is similar to Genghis Khan and his ilk (in this affair), who take as their loyal friends the one in agreement with them and the one who oppose them as a rebellious enemy; rather it is obligated on them and their followers (i.e. the teachers) to fulfil the covenant of Allah and His Messenger by obeying Allah and His Messenger, doing that which Allah and His Messenger have commanded, declare unlawful that which Allah and His Messenger have declared unlawful, and preserve the rights of the teachers in the manner commanded by Allah and His Messenger. So, if one’s teacher is oppressed, he should help him; but if the teacher is the oppressor, he should not aid him in his act of oppression; rather he forbids him from it, as it has been established in the authentic books of hadith that the Prophet [peace and blessings of Allah be upon him] said, “Help your brother, whether he is an oppressor or he is an oppressed one. People asked, “O Allah’s Messenger! It is all right to help him if he is oppressed, but how should we help him if he is an oppressor?” The Prophet said, “By preventing him from oppressing others.” [Al-Bukhari 2444]

If an argument and dispute occurs between a teacher and another teacher, or between a student and another student, it is not permissible for anyone to help one of them until he knows the truth – neither to aid him based on ignorance nor desires; rather he he examines the affair, so if the truth becomes clear to him, he helps the one who deserves to be helped (due to him being upon the truth) against the one upon error – regardless whether the one who deserves to be helped is one of his companions or the companion of someone else, or whether the one upon error is one of his companions or the companion of someone else. Therefore, the aim is only to worship Allah alone, obedience to Allaah’s Messenger, adherence to truth and establishment of justice. Allah, The Most High, said:

يا أيها الذين آمنوا كونوا قوامين بالقسط شهداء لله ولو على أنفسكم أو الوالدين والأقربين، إن يكن غنياً أو فقيراً فالله أولى بهما، فلا تتبعوا الهوى أن تعدلوا وإن تلووا أو تعرضوا فإن الله كان بما تعملون خبيراً

O you who believe! Stand out firmly for justice, as witnesses to Allah; even though it be against yourselves, or your parents, or your kin, be he rich or poor, Allah is a Better Protector to both (than you). So follow not the lusts (of your hearts), lest you may avoid justice, and if you distort your witness or refuse to give it, verily, Allah is Ever Well-Acquainted with what you do. [An-Nisaa. 135] [2]

[1] An Excerpt from Tafsir As-Sa’di

[2] Majmu Al-Fataawaa. 28/15-17. paraphrased