The Messenger of Allah ﷺ said, "The martyr has six privileges with Allah," and among them he mentioned, "He is protected from the punishment of the grave."
عن رسول الله ﷺ قال: للشهيد عند الله ست خصال وذكر منها: ويجار من عذاب القبر.
Ibn Majah (2799) narrated it from Hisham bin Ammar, who said, Ismail bin Ayyash told us, who said, Buhayr bin Saad told me, from Khalid bin Madan, from Miqdam bin Mad Yakrib, and he related it. Its isnad is hasan because of Ismail bin Ayyash, for his hadith is hasan when he narrates from the people of his own region, the Levantines, and Buhayr bin Saad is one of them, from Hims. Imam Ahmad (17182) also narrated it by this same route, and Baqiya bin Walid followed him in narrating it, transmitting it from Buhayr bin Saad with the same isnad. Tirmidhi (1663) narrated it and said, "Hasan sahih gharib."I say, it contains Baqiya bin Walid, who is a mudallis, but his use of "an" (indirect transmission) from Buhayr bin Saad is accepted, as Ibn Abdul-Hadi stated in his commentary on Ilal Ibn Abu Hatim.The hadith has other chains from the narration of Ismail bin Ayyash, for he attributed it once to the musnad of Ibn Mad Yakrib, and another time to the musnad of Ubada bin Samit. Imam Ahmad (17183) narrated it from Hakam bin Nafi, who said, Ibn Ayyash told us, from Buhayr bin Saad, from Khalid bin Madan, from Kathir bin Mura, from Ubada bin Samit, from the Prophet ﷺ.It may be that he heard this hadith from his teacher Buhayr bin Saad through two different routes, since he was from Hims, and his hearing from the people of his own region is sahih, so there is no inconsistency in the isnad.