Jami` at-Tirmidhi 1352
Kathir bin 'Amr bin 'Awf Al-Muzani narrated from his father, from his grandfather, that the Messenger of Allah ﷺ said:
"Reconciliation is allowed among the Muslims, except for reconciliation that makes the lawful unlawful, or the unlawful lawful. And the Muslims will be held to their conditions, except the conditions that make the lawful unlawful, or the unlawful lawful."
حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ الْخَلاَّلُ، حَدَّثَنَا أَبُو عَامِرٍ الْعَقَدِيُّ، حَدَّثَنَا كَثِيرُ بْنُ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ عَوْفٍ الْمُزَنِيُّ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " الصُّلْحُ جَائِزٌ بَيْنَ الْمُسْلِمِينَ إِلاَّ صُلْحًا حَرَّمَ حَلاَلاً أَوْ أَحَلَّ حَرَامًا وَالْمُسْلِمُونَ عَلَى شُرُوطِهِمْ إِلاَّ شَرْطًا حَرَّمَ حَلاَلاً أَوْ أَحَلَّ حَرَامًا " .
قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ .