It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: If the one who drinks water while standing were to know what is entering his stomach, he would vomit it out immediately.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7808
Hadith Gradingحکم دارالسلام:حديث صحيح، م: 2026، وهذا إسناد ضعيف لإبهام الراوي عن أبي هريرة.