Abu Hurairah (RAA) narrated that The Messenger of Allah (ﷺ) said:
"Whichever town you take peacefully (they surrendered without, fighting), and stay therein, you have a share in it (in whatever is obtained from it); and whichever town disobeys Allah and His Messenger, a fifth of (its booty) goes to Allah and His Messenger and what remains is yours. Related by Muslim.
English reference: Book 11, Hadith 1345
Arabic reference: Book 11, Hadith 1319