The Messenger of Allah ﷺ said, "When a man says to his brother, 'You disbeliever,' one of the two has incurred it."Ikrima bin Ammar reported from Yahya from Abdullah bin Yazid, who heard Abu Salama, who heard Abu Hurayra, from the Prophet ﷺ.
حدثنا محمد وأحمد بن سعيد قالا حدثنا عثمان بن عمر أخبرنا علي بن المبارك عن يحيى بن أبي كثير عن أبي سلمة
أن رسول الله ﷺ قال إذا قال الرجل لأخيه يا كافر فقد باء به أحدهما وقال عكرمة بن عمار عن يحيى عن عبد الله بن يزيد سمع أبا سلمة سمع أبا هريرة عن النبي ﷺ
Bukhari reported the hadith of Ali bin Mubarak, from Yahya, from Abu Salama, from Abu Hurairah, that the Prophet, peace and blessings be upon him and his family, said, "If a man says to his brother, 'O disbeliever,' one of the two deserves it."Bukhari said, Ikrima bin Ammar said, from Yahya, from Abdullah bin Yazid, who heard Abu Salama, who heard Abu Hurairah, from the Prophet, peace and blessings be upon him and his family, something similar.Abu Hasan said, Yahya bin Abu Kathir practices tadlis frequently, and it seems that the statement of Ikrima bin Ammar is more likely to be correct, because he added a man, and he is trustworthy.
Hafiz said in the introduction to Fath al-Bari, page 379 (Salafiyyah edition), after mentioning Daraqutni's statement, "I say, Bukhari transmitted Ikrima's route as a suspended chain, so for him it remains only a possibility. And Allah knows best." End of quote.He also said in Fath al-Bari, volume 10, page 515, that Bukhari's approach indicates that the addition of Abdullah bin Yazid between Yahya and Abu Salama in this suspended narration did not undermine the narration of Ali bin Mubarak from Yahya, in which Abdullah bin Yazid is not mentioned. This is either because it is possible that Yahya heard it from Abu Salama through an intermediary and then also heard it from Abu Salama directly, or because Bukhari did not give weight to the addition made by Ikrima bin Ammar, due to the weakness of his memory in Bukhari's assessment.
Daraqutni criticized Bukhari for including the narration of Ali bin Mubarak, saying, "Yahya bin Abu Kathir is a mudallis, and Ikrima added an extra man in it." The truth is that Bukhari cannot be faulted for something like this, because the defect was not hidden from him. Rather, he knew it, made it apparent, and indicated that it does not invalidate the hadith. This seems to be because the basis of the hadith is well known and its text is well established, having been narrated through several routes. From this we learn that defects vary in degree, and that when something whose surface appearance suggests a flaw is reinforced by other support, the flaw is removed from it. Allah knows best.I say, Ikrima bin Ammar does not match the standing of Ali bin Mubarak, especially since Hafiz mentioned in Taqrib, in the biographical entry on Ikrima, that there is confusion in his narration from Yahya bin Abu Kathir. Still, the issue remains with the hadith that Yahya is a mudallis and did not explicitly state that he heard it directly. Bukhari's justification for including it is that the basis of the hadith is well known and its text is well established, as Hafiz stated. Allah knows best.