From Sahih Bukhari (Hadith 2981):
Narrated Suwaid bin An-Nu`man:That he went out in the company of the Prophet (ﷺ) during the year of Khaibar (campaign) till they reached a place called As-Sahba', the lower part of Khaibar. They offered the `Asr prayer (there) and the Prophet asked for the food. Nothing but Sawiq was brought to the Prophet. So, they chewed it and ate it and drank water. After that the Prophet (ﷺ) got up, washed his mouth, and they too washed their mouths and then offered the prayer
Reference: Bukhari 2981