Hadith 15990
It is narrated from Sayyiduna Suwaid bin Nu'man that in the year of the conquest of Khaybar, we set out with the Prophet (peace be upon him). When we reached the place of Sahba and the Prophet (peace be upon him) had led the Asr prayer, food was requested, but only sattu (barley flour) was presented as food. The people ate it and drank water over it. Then, after rinsing his mouth with water, the Prophet (peace be upon him) led them in prayer while standing.