Ja'far bin Muhammad (may Allah have mercy on them both) narrates from his father that the Messenger of Allah (peace and blessings be upon him) "judged by an oath along with a single witness."
Isma'il bin Ja'far added in his narration: And Ali (may Allah be pleased with him) judged by it in Iraq. A group narrated it in this way from Ja'far bin Muhammad as mursal (without the Companion), while Abd al-Wahhab bin Abd al-Majid al-Thaqafi, who is one of the trustworthy narrators, narrated it from Ja'far bin Muhammad, from his father, from Jabir bin Abdullah, from the Prophet (peace and blessings be upon him) with a connected chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20652