Narrated Suwaid bin An-Nu`man: That he went out in the company o; 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.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، قَالَ سَمِعْتُ يَحْيَى، قَالَ أَخْبَرَنِي بُشَيْرُ بْنُ يَسَارٍ، أَنَّ سُوَيْدَ بْنَ النُّعْمَانِ ـ رضى الله عنه ـ أَخْبَرَهُ أَنَّهُ، خَرَجَ مَعَ النَّبِيِّ صلى الله عليه وسلم عَامَ خَيْبَرَ، حَتَّى إِذَا كَانُوا بِالصَّهْبَاءِ ـ وَهْىَ مِنْ خَيْبَرَ وَهْىَ أَدْنَى خَيْبَرَ ـ فَصَلَّوُا الْعَصْرَ، فَدَعَا النَّبِيُّ صلى الله عليه وسلم بِالأَطْعِمَةِ، فَلَمْ يُؤْتَ النَّبِيُّ صلى الله عليه وسلم إِلاَّ بِسَوِيقٍ، فَلُكْنَا فَأَكَلْنَا وَشَرِبْنَا، ثُمَّ قَامَ النَّبِيُّ صلى الله عليه وسلم فَمَضْمَضَ وَمَضْمَضْنَا، وَصَلَّيْنَا.
sunnah.com