Hadith 2168
Sayyiduna Abu Humayd As-Sa'idi (may Allah be pleased with him) said: I brought milk to the Messenger of Allah (peace and blessings be upon him), so he said: "Why did you not cover this (vessel)? You could have placed even a stick across its top."
Hadith 2169
Sayyiduna Abu Hurairah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings of Allah be upon him) commanded us to cover water, to tie the mouth of the water-skin, and to turn vessels upside down.