مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 4299
Foods
Covering Vessels and other things - Section 1
وَعَنْهُ قَالَ: جَاءَ أَبُو حُمَيْدٍ رَجُلٌ مِنَ الْأَنْصَارِ مِنَ النَّقِيعِ بِإِنَاءٍ مِنْ لَبَنٍ إِلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أَلَّا خَمَّرْتَهُ وَلَوْ أنْ تعرِضَ عليهِ عوداً»
He told that when Abu Humaid, one of the Ansar, brought a vessel of milk to the Prophet (ﷺ) from an-Naqi'* the Prophet (ﷺ) said, “Why did you not cover it up, even by putting a piece of wood on it?” *A place in the wadi al-'Aqiq where camels which had been given in sadaqa were kept. (Bukhari and Muslim.)
Mishkat al-Masabih, 4299مُتَّفق عَلَيْهِ (الألباني)