1223 – Ibn ʿAbbās (may Allah be pleased with him) related that the Prophet (peace and blessings be upon him) said: “Were people to be awarded simply on the basis of their claims, some would demand the lives and property of others. Rather, the oath is incumbent upon the one against whom the claim is lodged.” Agreed upon.
Al-Bayhaqī, with an authentic chain, adds the wording: “The bayyina (conclusive proof) rests upon the claimant, and the yamīn (oath) is upon the one who denies.” (1)

Degree of authenticity:
The extra wording recorded by al-Bayhaqī has an authentic chain, as the author—may Allah have mercy on him—stated. Al-Nawawī judged it sound in his Forty Ḥadith, and the same ruling was given by Ibn al-Ṣalāḥ. Ibn Rajab said: “Imam Aḥmad and Abū ʿUbayd cited this ḥadith as legal evidence; they would not have done so unless, in their view, it was authentic and fit for proof.” He then remarked, “Many other aḥādīth convey this very meaning,” and listed them in his commentary on the Forty Ḥadith.

Key terms in the ḥadith
• bayyina: linguistically, from bayana—“to become clear”; it signifies a manifest sign. In Sharīʿa usage, it denotes whatever discloses and makes the truth apparent.
• yamīn (oath): in ordinary speech it conveys the idea of strength; from it comes the term for the right hand. Technically, it is the affirmation of what one swears to by invoking something exalted, in a prescribed manner. It is called an “oath” because the swearer extends his right hand and strikes it upon the right hand of his counterpart.