The Messenger of Allah ﷺ said, "The Hour will not come until two great factions fight each other, with a tremendous slaughter between them, though their claim is one and the same."
قال رسول الله ﷺ: لا تقوم الساعة حتى تقتتل فئتان عظيمتان، وتكون بينهما مقتلة عظيمة، ودعواهما واحدة.
Bukhari narrated it in the Book of Virtues (3609), and Muslim in the Book of Tribulations and Signs of the Hour (157:17), from Muhammad bin Rafi, who said, Abdul-Razzaq narrated to us, who said, Mamar narrated to us, from Hammam bin Munabbih, who said, this is what Abu Hurairah narrated to us from the Messenger of Allah. He then related several hadiths, among them this one.