From Sahih Muslim (Hadith 7327):
Abu Huraira reported that Allah's Messenger (ﷺ) said:Kisra (Khusrau king of Persia) would die and Qaisar (Ceasar King of Rome) would die; there would be no Qaisar after him, but, by the One in Whose Hand is my life, you would spend their treasures in the cause of Allah. This hadith has been transmitted on the authority of Zuhri
Reference: Muslim 7327