The people doubted whether the Prophet (ﷺ) was observing the fast on the Day of `Arafat, so I sent something for him to drink and he drank it.
Sahih al-Bukhari Book 25, Hadith 139
← Previous Hadith I offered (only a) two rak`at prayer with the Prophet (at Mina), and similarly with Abu Bakr and with `Umar, and then you d offered in opinions. Wish that I would be lucky enough to have two of the four rak`at accepted (by Allah).

Sahih al-Bukhari Book 25, Hadith 138 Next Hadith → I asked Anas bin Malik while we were proceeding from Mina to `Arafat, "What do you use to do on this day when you were with Allah's Messenger (ﷺ) ?" Anas said, "Some of us used to recite Talbiya and nobody objected to that, and others used to recite Takbir and nobody objected to that."

Sahih al-Bukhari Book 25, Hadith 140