I met my uncle carrying a banner, so I asked him, "Where are you headed?"He replied, "The Messenger of Allah ﷺ has sent me to a man who married his father's wife. He ordered me to strike off his neck and seize his property."
لقيت عمي ومعه راية، فقلت له: أين تريد؟ قال: بعثني رسول الله ﷺ إلى رجل نكح امرأة أبيه، فأمرني أن أضرب عنقه، وآخذ ماله.
Abu Dawud (4457), Nasai (3332), Ibn Jarud (681), and Hakim (4/357), and from his route Bayhaqi (7/162) and Daraqutni in Ilal (6/22), all narrated it, all of them by way of Zayd bin Abu Unaysa, from Adi bin Thabit, from Yazid bin Bara, from his father, and he mentioned it. Its isnad is sahih.This is what Abu Hatim and Abu Zura confirmed as correct, as stated in Ilal (1/403), and they said, "And his maternal uncle is Abu Burda, though some say, 'from his paternal uncle Abu Burda.'" Abu Burda is Ibn Niyar, with the noon vowelled with a kasra, a companion whose name was Hani. It is also said his name was Harith bin Amr, and it is also said Malik bin Hubayra.There is disagreement regarding Adi bin Thabit, as Tirmidhi (1362) stated after narrating it from Ashath, from Adi bin Thabit, from Bara, who said, "My maternal uncle Abu Burda bin Niyar passed by me carrying a banner," and then he mentioned the hadith. Ibn Majah (2607) also narrated it by this route. Tirmidhi said, "The hadith of Bara is a hasan gharib hadith. Muhammad bin Ishaq narrated this hadith from Adi bin Thabit, from Abdullah bin Yazid, from Bara. This hadith has also been narrated from Ashath, from Adi, from Yazid bin Bara, from his father, and it has been narrated from Ashath, from Adi, from Yazid bin Bara, from his maternal uncle, from the Prophet ﷺ." This concludes Tirmidhi's statement.As for the hadith of Adi from Yazid bin Bara, Bayhaqi narrated it (8/238). It has become clear from this that Ashath, who is Ibn Sawwar Kindi, and who is daif by the consensus of the scholars, was inconsistent in his isnad. So I do not know whether Tirmidhi came across other chains of transmission or not. Likewise, Daraqutni mentioned this disagreement in Ilal (6/20), but he did not favor one view the way Abu Hatim and Abu Zura did.The hadith has another isnad, which is what Nasai (3331), Ibn Hibban (4112), and Hakim (2/191) recorded, all of them from the hadith of Suddi, from Adi bin Thabit, from Bara, in which it states, "I met my maternal uncle Abu Burda," and then he mentioned the hadith. Hakim said, "Sahih according to the criterion of Muslim."As for his saying "my paternal uncle" in one narration and "my maternal uncle" in another, there is no contradiction between the two, for he may have been his paternal uncle through lineage and his maternal uncle through fosterage. Given that his name is explicitly stated to be Harith bin Amr, or Abu Burda bin Niyar, it appears that he was his maternal uncle rather than his paternal uncle.