Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
bayhaqi:11353 – Abū Ṭāhir al-Faqīh > Abū Ḥāmid b. Bilāl > Yaḥyá b. al-Rabīʿ al-Makkī > Sufyān > Idrīs al-Awdī > Akhraj

[Machine] This is a book that Omar sent to Abu Musa mentioning in it that reconciliation is permissible among people except if it makes the forbidden lawful or makes the lawful forbidden.  

البيهقي:١١٣٥٣ – أَخْبَرَنَا أَبُو طَاهِرٍ الْفَقِيهُ أنبأ أَبُو حَامِدِ بْنُ بِلَالٍ ثنا يَحْيَى بْنُ الرَّبِيعِ الْمَكِّيُّ ثنا سُفْيَانُ عَنْ إِدْرِيسَ الْأَوْدِيِّ قَالَ أَخْرَجَ إِلَيْنَا سَعِيدُ بْنُ أَبِي بُرْدَةَ كِتَابًا فَقَالَ

هَذَا كِتَابُ عُمَرَ ؓ إِلَى أَبِي مُوسَى فَذَكَرَهُ وَفِيهِ وَالصُّلْحُ جَائِزٌ بَيْنَ النَّاسِ إِلَّا صُلْحًا أَحَلَّ حَرَامًا أَوْ حَرَّمَ حَلَالًا  

See similar narrations below:

Collected by Ibn Ḥibbān

ذِكْرُ الْإِخْبَارِ عَنْ جَوَازِ الصُّلْحِ بَيْنَ الْمُسْلِمِينَ مَا لَمْ يُخَالِفِ الْكِتَابَ أَوِ السُّنَّةَ أَوِ الْإِجْمَاعَ

ibnhibban:5091 – Muḥammad b. al-Fatḥ al-Simsār Bisamarqand > ʿAbdullāh b. ʿAbd al-Raḥman al-Dārimī > Marwān b. Muḥammad al-Ṭāṭarī > Sulaymān b. Bilāl > Kathīr b. Zayd > al-Walīd b. Rabāḥ > Abū Hurayrah

“I heard the Messenger of Allah ﷺ say: 'Reconciling between Muslims is permissible, except reconciliation that forbids something that is allowed, or allows something that is forbidden.'” (Using translation from Ibn Mājah 2353)   

ابن حبّان:٥٠٩١ – أَخْبَرَنَا مُحَمَّدُ بْنُ الْفَتْحِ السِّمْسَارُ بِسَمَرْقَنْدَ قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَبْدِ الرَّحْمَنِ الدَّارِمِيُّ قَالَ حَدَّثَنَا مَرْوَانُ بْنُ مُحَمَّدٍ الطَّاطَرِيُّ قَالَ حَدَّثَنَا سُلَيْمَانُ بْنُ بِلَالٍ حَدَّثَنِي كَثِيرُ بْنُ زَيْدٍ عَنِ الْوَلِيدِ بْنِ رَبَاحٍ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ «الصُّلْحُ جَائِزٌ بَيْنَ الْمُسْلِمِينَ إِلَّا صُلْحًا أَحَلَّ حَرَامًا أَوْ حَرَّمَ حَلَالًا»