Some people were disputing in her presence on the day of Arafah about whether the Messenger of Allah ﷺ was fasting.Some said, "He is fasting."Others said, "He is not fasting."So she sent him a cup of milk while he was standing on his camel, and he drank it.
أن ناسا تماروا عندها يوم عرفة في صيام رسول الله ﷺ، فقال بعضهم: هو صائم. وقال بعضهم: ليس بصائم، فأرسلت إليه بقدح لبن- وهو واقف على بعيره- فشرب.
Malik related it in Hajj (132) from Abu Nadr, freedman of Umar bin Ubaydullah, from Umayr, freedman of Abdullah bin Abbas, from Umm Fadl, and he mentioned it. Bukhari related it in Hajj (1661), and Muslim in Fasting (1132:110), both by way of Malik, in like manner.Umm Fadl's name was Lubaba bint Harith al-Hilaliyya, sister of Maymuna, wife of the Prophet ﷺ, and wife of Abbas. She was among the earliest converts to Islam.