From Sahih Bukhari (Hadith 3120):
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "When Khosrau is ruined, there will be no Khosrau after him; and when Caesar is ruined, there will be no Caesar after him. By Him in Whose Hands my life is, you will spend their treasures in Allah's Cause
Reference: Bukhari 3120