The Messenger of Allah ﷺ said, "The defendant has the greater right to take the oath when there is no evidence."
قال رسول الله ﷺ: المدعى عليه أولى باليمين إذا لم تكن بينة.
Abdul-Razzaq narrated it in Musannaf (15184) from Ibn Jurayj, from Amr bin Shuayb, from his father, from his grandfather, who said, and he related it. Its isnad is hasan because of Amr bin Shuayb and his father, for the two of them make a hadith hasan.As for what Tirmidhi narrated (1341) via the route of Muhammad bin Ubaydullah, from Amr bin Shuayb, from his father, from his grandfather, that the Prophet ﷺ said, "The burden of proof is on the claimant, and the oath is on the one who denies," its isnad is daif. Tirmidhi said, "This is a hadith in whose isnad there is criticism, and Muhammad bin Ubaydullah Arzami is judged weak in hadith on account of his memory. Ibn Mubarak and others declared him daif."I say, it is as he said, except that the hadith is hasan by way of the first isnad.