Sunan Ibn Majah, Chapter: The Chapters of Purification and its Sunnah

that they went out with the Messenger of Allah (saw) to Khaibar. When they reached As-Sahba (a place near Khaibar), he performed Asr (Afternoon prayer), then he called for food, but no food was brought except for Sawiq.* So they ate that and drank, and then he called for water and rinsed his mouth, then he stood up and led us for Maghrib (Sunset) prayer." (Sahih) *A kind of mush of wheat or barley.