It was narrated that 'Abdullah bin Awfa said: "On the Day of khaiber we caught some donkeys outside the village and we cooked them. Then the caller of the Prophet (ﷺ) called out: 'The Messenger of Allah (ﷺ) has forbidden the flesh of donkeys, so turn over your cooking pots with whatever is in them.' So we turned them over."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ يَزِيدَ الْمُقْرِئُ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي إِسْحَاقَ الشَّيْبَانِيِّ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي أَوْفَى، قَالَ أَصَبْنَا يَوْمَ خَيْبَرَ حُمُرًا خَارِجًا مِنَ الْقَرْيَةِ فَطَبَخْنَاهَا فَنَادَى مُنَادِي النَّبِيِّ صلى الله عليه وسلم إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَدْ حَرَّمَ لُحُومَ الْحُمُرِ فَأَكْفِئُوا الْقُدُورَ بِمَا فِيهَا . فَأَكْفَأْنَاهَا .
sunnah.com