Musnad Abu Ya'la al-Mawsili 105:25

Wahb ibn Baqiyyah narrated to us, Khalid narrated to us, from ‘Ata’, from Maysarah and Abu al-Bakhtari, that ‘Ammar, on the day of Siffin, began to fight but was not killed. He came to ‘Ali and said, "O Commander of the Faithful, is this not such and such a day?" He said, "Go away from me." He said that repeatedly. Then milk was brought to him, and he drank it. ‘Ammar said, "Indeed, this is the last drink I shall drink from the world." Then he advanced and fought until he was killed.