The Messenger of Allah ﷺ ruled that a case may be decided on the basis of a single witness together with the oath of the claimant.
أن رسول الله ﷺ قضى باليمين مع الشاهد الواحد.
Abu Dawud (3610) narrated it from Ahmad bin Abu Bakr Abu Musab Zuhri, who said, Darawardi told us, from Rabia bin Abu Abdul-Rahman, from Suhayl bin Abu Salih, from his father, from Abu Hurairah, and he related it.Abu Dawud said, "Rabi bin Sulayman the muezzin added, in this hadith, he said, Shafii informed us, from Abdul-Aziz, who said, I mentioned that to Suhayl, and he said, Rabia informed me of it, and he is trustworthy in my view, that I had told it to him, but I do not remember it myself. Abdul-Aziz said, Suhayl had suffered an illness that took away some of his memory, and he forgot some of his hadiths. So afterward Suhayl would narrate it from Rabia from him, from his father."Then Abu Dawud also narrated it from the hadith of Sulayman bin Bilal, from Rabia, with the chain of Abu Musab and its meaning. Sulayman said, "I met Suhayl and asked him about this hadith, and he said, I do not know it. I said to him, Rabia informed me of it from you. He said, If Rabia informed you of it from me, then narrate it from Rabia from me."Among those who narrated it through the route of Abdul-Aziz bin Muhammad Darawardi, from Rabia, are Ibn Majah (2368) and Tirmidhi (1343). Tirmidhi added, "Rabia said, and the son of Saad bin Ubada informed me, he said, We found in the book of Saad that the Prophet ﷺ ruled that an oath be taken together with a witness." He said, "The hadith of Abu Hurairah is hasan gharib."Among those who narrated it from the hadith of Sulayman bin Bilal, from Rabia bin Abu Abdul-Rahman, are Ibn Jarud (1007), Ibn Hibban (5072), and Bayhaqi (10/168). Hafiz bin Hajar said in Fath al-Bari (5/282), "Its narrators are Madinans and trustworthy, and it does not harm it that Suhayl forgot it after having narrated it to Rabia, because after that he would narrate it from Rabia from himself, from his father." Abu Hatim and Abu Zura also graded it sahih, as mentioned in al-Ilal (1/469).This hadith was also narrated from Suhayl bin Abu Salih by someone other than Rabia bin Abu Abdul-Rahman, among them Muhammad bin Abdul-Rahman Muafiri, a trustworthy Madinan, who heard Suhayl bin Abu Salih narrating from his father, from Abu Hurairah, and he related the hadith. Bayhaqi narrated it (10/169) and said, "It has also been narrated through another route from Abu Hurairah." Then he mentioned some of these routes.It is reported from Imam Ahmad that he said, "There is no hadith in this chapter, meaning the ruling of an oath together with a witness, more sahih than this one."As for Tirmidhi's statement, "the son of Saad bin Ubada informed me," this is what Ahmad (2246), Tabarani in al-Kabir (5362), and Bayhaqi (10/171) all narrated, all of them through the route of Sulayman bin Bilal, from Rabia bin Abu Abdul-Rahman, from Ismail bin Amr bin Qays bin Saad bin Ubada, from his father, that they found in the books, or in the book, of Saad bin Ubada, that the Messenger of Allah ﷺ ruled that an oath be taken together with a witness.Shafii narrated it in al-Umm (6/254), and Bayhaqi through his route, from Abdul-Aziz bin Muhammad Darawardi, from Rabia bin Abu Abdul-Rahman, from Saeed bin Amr bin Shurahbil bin Saeed bin Saad bin Ubada, from his father, from his grandfather, who said, "We found in the books of Saad that the Messenger of Allah ﷺ ruled that an oath be taken together with a witness."Shafii said, "Abdul-Aziz bin Muttalib mentioned, from Saeed bin Amr, from his father, who said, We found in the books of Saad bin Ubada, Saad bin Ubada bearing witness, that the Messenger of Allah ﷺ ordered Amr bin Hazm to rule that an oath be taken together with a witness."The hadith has other chains of transmission. See Minna Kubra (9/139).