"The Prophet broke (the fast) of Arafah, Umm Fadl sent him some milk to drink."
Jami` at-Tirmidhi Book 8, Hadith 69
← Previous Hadith the Prophet said: "Fast the Day of Arafah, for indeed I anticipate that Allah will forgive (the sins) of the year after it, and the year before it."

Jami` at-Tirmidhi Book 8, Hadith 68 Next Hadith → "Ibn Umar was asked about fasting (the Day of) Arafah (at Arafat). He said: 'I performed Hajj with the Prophet, and he did not fast it, and with Abu Bakr, and he did not fast it, and with Umar, and he did not fast it, and with Uthman, and he did not fast it. I do no fast it, nor order it nor forbid it."

Jami` at-Tirmidhi Book 8, Hadith 70