رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 771
The Book About the Etiquette of Eating
Permission to Drink While Standing
وَعَنْ أبى هُرَيْرَةَ رضى اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : لَا يَشْرَبَنَّ أَحَدٌ مِنْكُمْ قَائِمًا، فَمَنْ نسى فَلْيَسْتَقِئْ". ((رَوَاهُ مُسْلِم))
Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said, "None of you should drink standing; and if any one forgets, he must vomit." [Muslim].
Riyad as-Salihin, 771