Prohibition of injustice تحريم الظلم
Abu Dharr reported: The Messenger of Allah, peace and blessings be upon him, said:
قال الله تبارك وتعالى يَا عِبَادِي إِنِّي حَرَّمْتُ الظُّلْمَ عَلَى نَفْسِي وَجَعَلْتُهُ بَيْنَكُمْ مُحَرَّمًا فَلَا تَظَالَمُوا
Allah Almighty said: O My servants, I have forbidden injustice for Myself and I have forbidden it among you, so do not oppress one another.
From Ṣaḥīḥ Muslim 2577, Grade: Sahih
Jabir reported: The Messenger of Allah, peace and blessings be upon him, said:
أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتَّى يَقُولُوا لَا إِلَهَ إِلَّا اللَّهُ فَإِذَا قَالُوا لَا إِلَهَ إِلَّا اللَّهُ عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلَّا بِحَقِّهَا وَحِسَابُهُمْ عَلَى اللَّهِ
I have been commanded to fight the people until they say there is no God but Allah. If they say there is no God but Allah, then they will be granted protection from me for their lives and property, except by right of justice, and their reckoning is with Allah.
From Ṣaḥīḥ Muslim 21, Grade: Sahih
Enjoining good and forbidding evil الأمر بالمعروف والنهي عن المنكر
Abu Sa’id al-Khudri reported: The Messenger of Allah, peace and blessings be upon him, said:
مَنْ رَأَى مِنْكُمْ مُنْكَرًا فَلْيُغَيِّرْهُ بِيَدِهِ فَإِنْ لَمْ يَسْتَطِعْ فَبِلِسَانِهِ فَإِنْ لَمْ يَسْتَطِعْ فَبِقَلْبِهِ وَذَلِكَ أَضْعَفُ الْإِيمَانِ
Whoever among you sees evil, let him change it with his hand. If he is unable to do so, then with his tongue. If he is unable to do so, then with his heart, and that is the weakest level of faith.
Source: Ṣaḥīḥ Muslim 49, Grade: Sahih
Sufyan al-Thawri, may Allah have mercy on him, said:
لا يَأْمُرُ بِالْمَعْرُوفِ وَلا يَنْهَى عَنِ الْمُنْكَرِ إِلا مَنْ كَانَ فِيهِ خِصَالٌ ثَلاثٌ رَفِيقٌ بِمَا يَأْمُرُ رَفِيقٌ بِمَا يَنْهَى عَدْلٌ بِمَا يَأْمُرُ عَدْلٌ بِمَا يَنْهَى عَالِمٌ بِمَا يَأْمُرُ عَالِمٌ بِمَا يَنْهَى
There is no enjoining good or forbidding evil except for one who has three qualities: gentleness in what he enjoins and forbids, justice in what he enjoins and forbids, and knowledge of what he enjoins and forbids.
Source: al-Amr bil-Maʻrūf lil-Khallāl 32
And Al-Qadi Abu Ya’la said:
لَا يَأْمُرُ بِالْمَعْرُوفِ وَيَنْهَى عَنْ الْمُنْكَرِ إلَّا مَنْ كَانَ فَقِيهًا فِيمَا يَأْمُرُ بِهِ فَقِيهًا فِيمَا يَنْهَى عَنْهُ رَفِيقًا فِيمَا يَأْمُرُ بِهِ رَفِيقًا فِيمَا يَنْهَى عَنْهُ حَلِيمًا فِيمَا يَأْمُرُ بِهِ حَلِيمًا فِيمَا يَنْهَى عَنْهُ
No one may enjoin good and forbid evil unless he understands what he enjoins and forbids, he is gentle in what he enjoins and forbids, and he shows forbearance in what he enjoins and forbids.
Source: al-Amr bil Ma’rūf li-Ibn Taymīyyah 1/20-21