Sayyiduna Suwayd bin al-Nu'man (may Allah be pleased with him) said: We set out with the Messenger of Allah (peace and blessings be upon him) in the year of Khaybar. When we reached al-Sahba' and had prayed Asr, the Prophet (peace and blessings be upon him) called for the people's provisions. They brought sawiq (barley meal), and everyone ate and drank. Then the Messenger of Allah (peace and blessings be upon him) stood up for the Maghrib prayer; he (peace and blessings be upon him) rinsed his mouth and the people rinsed their mouths too, and they prayed and did nothing (no ablution) beyond that.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6427