It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) forbade drinking water directly from the mouth of a water-skin. The narrator of the hadith, Ayyub, says that he was informed that a man drank water by putting his mouth to the mouth of a water-skin, and a snake came out of it.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7153