Musnad Ahmad 27:774

Waki’ narrated to us, Sufyan narrated to us, from Abu Ishaq, from al-Najrani, from Ibn Umar, who said: A drunkard was brought to the Messenger of Allah, peace and blessings of Allah be upon him, and he struck him with the prescribed punishment. Then he said: "What is your drink?" He said: "Raisins and dates." He said: "Do not mix them; each one of them is sufficient [as a substitute] for the other."