Jami` at-Tirmidhi 1352
جامع الترمذي#1352SahihKathir 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih
In-book reference: 15:32