Jami` at-Tirmidhi 1403
جامع الترمذي#1403SahihNarrated Abu Hurairah:that the Prophet (ﷺ) said: "Indeed, whoever kills a Mu'ahid that has a covenant from Allah and a covenant from His Messenger (ﷺ), then he has violated the covenant with Allah and the covenant of His Messenger, so he shall not smell the fragrance of Paradise; even though its fragrance can be sensed from the distance of seventy autumns
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: 16:19