Al-Harith bin Bilal bin al-Harith narrates from his father, Sayyiduna Bilal bin al-Harith (may Allah be pleased with him), that the Prophet (peace and blessings be upon him) gave judgement on the basis of an oath together with a single witness.
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1133