Musnad Ahmad 5:206

Yahya ibn Adam narrated to us, from Sufyan ibn Sa'id, from Abd al-Rahman ibn al-Harith, from Zayd ibn Ali, from his father, from Ubayd Allah ibn Abi Rafi', from Ali, that the Messenger of Allah (may Allah bless him and grant him peace) came to the place of slaughter in Mina and said: "This is the place of slaughter, and all of Mina is a place of slaughter."