Sahih Muslim 1937 a
Shaibani reported:
I asked 'Abdullah b. Abu Aufa about (the lawfulness or unlawfulness of) the flesh of the domestic asses. He said: We experienced hunger on the Day of Khaibar as we were with the Messenger of Allah (ﷺ). We found domestic asses in the exterior of Medina. We slaughtered them and our earthen pots were boiling when the announcer of the Messenger of Allah (ﷺ) made an announcement that the earthen pots should be turned upside down and nothing of the flesh of the domestic asses should be eaten. I said: What kind of prohibition is it that he (the Holy Prophet) has made? He said: We discussed it amongst -ourselves. Some of us aaid that it has been declared unlawful for ever, (whereas others said) it has been declared unlawful since one-fifth (of the booty) has not been given (to the treasury, as is legally required).
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنِ الشَّيْبَانِيِّ، قَالَ سَأَلْتُ
 عَبْدَ اللَّهِ بْنَ أَبِي أَوْفَى عَنْ لُحُومِ الْحُمُرِ الأَهْلِيَّةِ، فَقَالَ أَصَابَتْنَا مَجَاعَةٌ يَوْمَ خَيْبَرَ وَنَحْنُ
 مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم وَقَدْ أَصَبْنَا لِلْقَوْمِ حُمُرًا خَارِجَةً مِنَ الْمَدِينَةِ فَنَحَرْنَاهَا
 فَإِنَّ قُدُورَنَا لَتَغْلِي إِذْ نَادَى مُنَادِي رَسُولِ اللَّهِ صلى الله عليه وسلم أَنِ اكْفَئُوا الْقُدُورَ وَلاَ
 تَطْعَمُوا مِنْ لُحُومِ الْحُمُرِ شَيْئًا فَقُلْتُ حَرَّمَهَا تَحْرِيمَ مَاذَا قَالَ تَحَدَّثْنَا بَيْنَنَا فَقُلْنَا حَرَّمَهَا
 أَلْبَتَّةَ وَحَرَّمَهَا مِنْ أَجْلِ أَنَّهَا لَمْ تُخَمَّسْ ‏.‏