From Sahih Bukhari (Hadith 2954):
Narrated Abu Hurairah (ra):Allah's Messenger (ﷺ) sent us on a military expedition telling us, "If you find such and such persons (he named two men from Quraish), burn them with fire." Then we came to bid him farewell, when we wanted to set out, he said: "Previously I ordered you to burn so-and-so and so-and-so with fire, but as punishment with fire is done by none except Allah, if you capture them, kill them, (instead)
Reference: Bukhari 2954