Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
muslim:1939 – Aḥmad b. Yūsuf al-Azdī > ʿUmar b. Ḥafṣ b. Ghiyāth from my father > ʿĀṣim > ʿĀmir > Ibn ʿAbbās

I do not know whether Messenger of Allah ﷺ prohibited (the eating of the domestic ass) due to the fact that they were the beasts of burden for the people, so he (the Holy Prophet) did not like their beasts of burden to be destroyed (as a matter of expediency), or he prohibited the use of the flesh of domestic asses (not as an expediency but as a law of the Shari'ah) on the Day of Khaibar.  

مسلم:١٩٣٩ – وَحَدَّثَنِي أَحْمَدُ بْنُ يُوسُفَ الأَزْدِيُّ حَدَّثَنَا عُمَرُ بْنُ حَفْصِ بْنِ غِيَاثٍ حَدَّثَنَا أَبِي عَنْ عَاصِمٍ عَنْ عَامِرٍ عَنِ ابْنِ عَبَّاسٍ قَالَ

لاَ أَدْرِي إِنَّمَا نَهَى عَنْهُ رَسُولُ اللَّهِ ﷺ مِنْ أَجْلِ أَنَّهُ كَانَ حَمُولَةَ النَّاسِ فَكَرِهَ أَنْ تَذْهَبَ حَمُولَتُهُمْ أَوْ حَرَّمَهُ فِي يَوْمِ خَيْبَرَ لُحُومَ الْحُمُرِ الأَهْلِيَّةِ  

See similar narrations below:

Collected by Bukhārī, Bayhaqī
bukhari:4227 – Muḥammad b. Abū al-Ḥusayn > ʿUmar b. Ḥafṣ from my father > ʿĀṣim > ʿĀmir > Ibn ʿAbbās

I do not know whether the Prophet ﷺ forbade the eating of donkey-meat (temporarily) because they were the beasts of burden for the people, and he disliked that their means of transportation should be lost, or he forbade it on the day of Khaibar permanently.  

البخاري:٤٢٢٧ – حَدَّثَنِي مُحَمَّدُ بْنُ أَبِي الْحُسَيْنِ حَدَّثَنَا عُمَرُ بْنُ حَفْصٍ حَدَّثَنَا أَبِي عَنْ عَاصِمٍ عَنْ عَامِرٍ عَنِ ابْنِ عَبَّاسٍ ؓ قَالَ

لاَ أَدْرِي أَنَهَى عَنْهُ رَسُولُ اللَّهِ ﷺ مِنْ أَجْلِ أَنَّهُ كَانَ حَمُولَةَ النَّاسِ فَكَرِهَ أَنْ تَذْهَبَ حَمُولَتُهُمْ أَوْ حَرَّمَهُ فِي يَوْمِ خَيْبَرَ لَحْمَ الْحُمُرِ الأَهْلِيَّةِ  

bayhaqi:19460 – Abū Ṭāhir al-Faqīh > Abū Bakr Muḥammad b. al-Ḥusayn al-Qaṭṭān > Aḥmad b. Yūsuf > ʿUmar b. Ḥafṣ b. Ghiyāth from my father > ʿĀṣim > ʿĀmir > Ibn ʿAbbās

[Machine] I do not know why the Messenger of Allah, ﷺ , prohibited it. Perhaps it was because it was burdensome for the people, so he disliked their burdens being taken away or prohibited them from eating the flesh of domesticated donkeys on the day of Khaybar.  

البيهقي:١٩٤٦٠ – وَقَدْ أَخْبَرَنَا أَبُو طَاهِرٍ الْفَقِيهُ أنبأ أَبُو بَكْرٍ مُحَمَّدُ بْنُ الْحُسَيْنِ الْقَطَّانُ ثنا أَحْمَدُ بْنُ يُوسُفَ ثنا عُمَرُ بْنُ حَفْصِ بْنِ غِيَاثٍ حَدَّثَنِي أَبِي عَنْ عَاصِمٍ عَنْ عَامِرٍ عَنِ ابْنِ عَبَّاسٍ ؓ قَالَ

لَا أَدْرِي أَنَهَى عَنْهُ رَسُولُ اللهِ ﷺ مِنْ أَجْلِ أَنَّهُ كَانَ حَمُولَةَ النَّاسِ فَكَرِهَ أَنْ تَذْهَبَ حَمُولَتُهُمْ أَوْ حَرَّمَهُ فِي يَوْمِ خَيْبَرَ لَحْمَ الْحُمُرِ الْأَهْلِيَّةِ  

رَوَاهُ الْبُخَارِيُّ فِي الصَّحِيحِ عَنْ مُحَمَّدِ بْنِ أَبِي الْحُسَيْنِ عَنْ عُمَرَ بْنِ حَفْصٍ وَرَوَاهُ مُسْلِمٌ عَنْ أَحْمَدَ بْنِ يُوسُفَ الْأَزْدِيِّ