On the authority of Abū Saʿīd al-Khudrī (may Allah be pleased with him), who said: The Messenger of Allah ﷺ forbade the bending-back of waterskins — meaning that their mouths be folded outwards and drunk from. Agreed upon.
١١٢ - باب كراهة الشرب من فم القربة ونحوها وبيان أنه كراهة تنزيه لا تحريم
On the authority of Abū Saʿīd al-Khudrī (may Allah be pleased with him), who said: The Messenger of Allah ﷺ forbade the bending-back of waterskins — meaning that their mouths be folded outwards and drunk from. Agreed upon.
And on the authority of Abū Hurayrah (may Allah be pleased with him), who said: The Messenger of Allah ﷺ forbade drinking from the mouth of a waterskin or a water-bag. Agreed upon.
And on the authority of Umm Thābit Kabshah bint Thābit, the sister of Ḥassān ibn Thābit (may Allah be pleased with them), who said: The Messenger of Allah ﷺ came in to me and drank from the mouth of a hanging waterskin while standing, so I got up [and went] to its mouth and cut it off. Reported by al-Tirmidhī, who said: "A good and sound hadith." She cut it off only so as to preserve the place of the mouth of the Messenger of Allah ﷺ, to seek blessing through it, and to protect it from being put to common use. This hadith is to be understood as establishing permissibility, while the two preceding hadiths establish what is more virtuous and more complete. And Allah knows best.