953 – Ibn ʿAbbās (may Allah be pleased with him) related that the Messenger of Allah ﷺ “ordered a man to place his hand over his mouth when taking the fifth oath and said, ‘It is binding.’” It was reported by Abū Dāwūd and al-Nasāʾī, and all the transmitters are trustworthy (1).

Degree of authenticity:
The chain of transmission is sound. Abū Dāwūd, al-Nasāʾī, al-Bayhaqī, and al-Ḥumaydī all recorded it through Sufyān → ʿĀṣim ibn Kulayb → his father → Ibn ʿAbbās. Al-Albānī declared the isnād authentic, and Ibn ʿAbd al-Hādī said in al-Muḥarrar that its chain is unobjectionable.

Vocabulary notes:
• fīh: originally fawh, as shown by the plural afwāh (“mouths”). It denotes the mouth of a human or an animal. Al-Miṣbāḥ notes that it is one of the rare words whose singular form does not resemble its plural. When joined to the first-person suffix it becomes fīy or famī; when annexed to other pronouns it is declined with letters. It is therefore one of the five nouns that take yāʾ in the genitive, alif in the accusative, and wāw in the nominative—provided the final mīm is dropped. If the mīm remains, it is declined with short vowels.
• mujibah (“binding”): meaning that it establishes and necessitates perpetual separation in this world, or severe punishment in the Hereafter.

Points derived from the ḥadith:
1 – Of the two parties engaged in liʿān, one is certainly lying, but it is unknown which one.