From Sahih Bukhari (Hadith 1661):
Narrated Um Al-Fadl bint Al Harith:On the day of `Arafat, some people who were with me, differed about the fasting of the Prophet (ﷺ) some said that he was fasting while others said that he was not fasting. So I sent a bowl full of milk to him while he was riding his camel, and he drank that milk
Reference: Bukhari 1661