It is narrated from Sayyiduna Suwayd bin al-Nu'man (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) set out towards Khaybar and stopped at a place near it called al-Sahba'. He (peace and blessings be upon him) asked the Companions for what remained of their provisions, and they brought him (peace and blessings be upon him) nothing but sawiq (barley meal). He (peace and blessings be upon him) mixed it (with water) and ate, then rinsed his mouth, stood up and led the Maghrib prayer, and did not perform fresh ablution.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6429