Narrated Abu Hurairah: The Prophet ﷺ said: Conciliation between Muslims is permissible. The narrator Ahmad added in his version: "except the conciliation which makes lawful unlawful and unlawful lawful. " Sulayman ibn Dawud added: The Messenger of Allah ﷺ said: Muslims are on (i. e. stick to) their conditions.
Hadith Referenceسنن ابي داود / كتاب الأقضية / 3594
Hadith Gradingالألبانی:حسن صحيح | زبیر علی زئی:إسناده حسن, مشكوة المصابيح (5246، 2923), رواه النسائي (3181 وسنده صحيح)
Hadith Takhrij« تفرد بہ أبوداود، (تحفة الأشراف: 14806)، وقد أخرجہ: مسند احمد (2/366) (حسن صحیح) »
Narrated 'Amr bin 'Auf al-Muzani (RA): Allah's Messenger (ﷺ) said: "Reconciliation is permissible between Muslims, except one which makes unlawful something which is lawful, or makes lawful something which is unlawful; and Muslims must abide by their conditions (which they have made), except for a condition which makes unlawful something which is lawful, or makes lawful something which is unlawful." [at-Tirmidhi reported it and graded it Sahih (authentic)]. However, the Hadith scholars criticized him (for grading this Hadith as Sahih) because the narration of Kathir bin 'Abdullah bin 'Amr bin 'Auf is weak. It is as though at-Tirmidhi considered it (reliable) due to its many chains of narration. Ibn Hibban declared the aforesaid Hadith to be Sahih (authentic) from the narration of Abu Hurairah (RA).