Musannaf Ibn Abi Shayba 28:1040

Waki’ narrated to us, he said: Sufyan narrated to us, from Abu Ishaq, from a man from Muzaynah or Juhaynah, he said: The Prophet, peace and blessings of Allah be upon him, heard a people saying in their battle cry, "O Haram (Sacred/Forbidden)!" So he said, "O Halal (Lawful/Permissible)!"