The Messenger of Allah ﷺ ruled with the oath together with a single witness. Jafar said, "My father said, 'Ali ruled by it in Iraq.'"Abu Abdul-Rahman said, "My father had struck out this hadith." He said, "No one agreed with Thaqafi in narrating it from Jabir, but I kept pressing him until he read it to me and wrote on it, 'It is sound.'"
حدثنا عبد الوهاب الثقفي عن جعفر عن أبيه
أن رسول الله ﷺ قضى باليمين مع الشاهد قال جعفر قال أبي وقضى به علي بالعراق قال أبو عبد الرحمن كان أبي قد ضرب على هذا الحديث قال ولم يوافق أحد الثقفي على جابر فلم أزل به حتى قرأه علي وكتب عليه هو صح
Its chain of transmission is sahih, but as Ibn Ahmad said, Ahmad struck it out, and there is significant disagreement among the jurists about it, because Abdul-Wahhab bin Abdul-Majid Thaqafi was the sole transmitter of it. The hadith is found in Tirmidhi 3/628, no. 1344, in the Book of Rulings, chapter on what has been said about the oath together with the witness, and he indicated that it was sahih, and Ibn Majah has it similarly at no. 2368.