Riyad us-Saliheen

Umm Thabit Kabshah (May Allah be pleased with her), daughter of Thabit (May Allah be pleased with him) and the sister of Hassan bin Thabit, the Prophet's poet) reported: The Messenger of Allah (ﷺ) visited me and drank some water from a hanging water-skin while he was in a standing posture. So, I stood up and cut off the mouth (of that water-skin).. An-Nawawi said that the reason why she did this was to preserve the part of the water-skin which the lips of Messenger of Allah (ﷺ) touched, gain blessings from it, and preserve it from dishonor. This narration is understood to show permissibility whereas the previous two narrations are to show what is better and closer to perfection. Allah knows best.