Hadith: There should be no harm or reciprocal harm

عَنْ أَبِي سَعِيدٍ سَعْدِ بْنِ مَالِكِ بْنِ سِنَانٍ الخُدْرِيّ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«لَا ضَرَرَ وَلَا ضِرَارَ».
[حسن] - [رواه ابن ماجه، والدارقطني، وغيرهما مسندًا] - [الأربعون النووية: 32]

Abu Sa‘īd Sa‘d ibn Mālik ibn Sinān al-Khudri (may Allah be pleased with him) reported that the Messenger of Allah (ﷺ) said:
"There should be no harm or reciprocal harm."
[Hasan] - [Narrated by Ibn Mājah, Ad-Dāraquṭnī, and others with a connected chain] - [Al-Arba‘oon An-Nawawiyyah (The Forty Hadith of An-Nawawiyyah) - 32]

Explanation

The Prophet (ﷺ) pointed out that we should avert harm from ourselves and from others in all its kinds and manifestations. It is equally impermissible for anyone to harm himself or others. It is also not permissible to respond to harm with harm, for harm will not be removed with harm except by way of legal retribution, without transgression.

Benefits from the Hadith

1. It is prohibited to respond to harm with more than its equivalent.
2. Allah did not enjoin upon His servants anything harmful to them.
3. The Hadīth represents a rule on the prohibition of harm and reciprocal harm by words, deeds, or lack of action.
4. One of the Sha‘i rules is that "harm should be removed", for the Shariah disapproves of harming and condemns harming.