Abu Dawud

(1) The meat of any animal whose predominant food is filth is prohibited to eat, whether that animal is a beast or a bird.

(2) From this hadith, it is also understood that riding an animal called "jallalah"—that is, an animal that subsists on eating filth—is prohibited.

(3) The meat of a domestic, i.e., tamed donkey is absolutely haram, whether it eats filth or not. However, riding it is permissible because it has been created specifically for riding and carrying loads. Its sweat, etc., is pure. But if any animal that eats filth to such an extent that its effects are noticeable in its flesh—for example, if the meat emits the smell of filth, its taste is spoiled, or its color changes—then not only is eating it haram, but riding such an animal is also prohibited, because the effects of filth will be present in its sweat as well, thus the sweat will be impure. The rider’s clothes will inevitably become contaminated with the animal’s sweat, and they too will become impure. Clothes touch the body, so the rider’s body will also become impure; therefore, riding is also prohibited. Sweat is produced from the flesh itself. If the flesh is impure, then the sweat is also impure. However, this ruling does not apply to animals that eat a small amount of filth, because animals cannot be restricted to purely clean food. The effects of minor filth do not reach the flesh, etc.

Benefit:
It is established from this hadith that merely taking an oath does not make the action obligatory; rather, if there is another action better than the one for which the oath was taken, then the better action should be done and the expiation (kaffarah) for the oath should be given.

﴿لَا يُؤَاخِذُكُمُ اللَّهُ بِاللَّغْوِ فِي أَيْمَانِكُمْ وَلَٰكِن يُؤَاخِذُكُم بِمَا عَقَّدتُّمُ الْأَيْمَانَ فَكَفَّارَتُهُ إِطْعَامُ عَشَرَةِ مَسَاكِينَ مِنْ أَوْسَطِ مَا تُطْعِمُونَ أَهْلِيكُمْ أَوْ كِسْوَتُهُمْ أَوْ تَحْرِيرُ رَقَبَةٍ فَمَن لَّمْ يَجِدْ فَصِيَامُ ثَلَاثَةِ أَيَّامٍ ذَٰلِكَ كَفَّارَةُ أَيْمَانِكُمْ إِذَا حَلَفْتُمْ وَاحْفَظُوا أَيْمَانَكُمْ كَذَٰلِكَ يُبَيِّنُ اللَّهُ لَكُمْ آيَاتِهِ لَعَلَّكُمْ تَشْكُرُونَ﴾ (al-Ma'idah 5:89)

“Allah does not call you to account for your unintentional oaths, but He calls you to account for those oaths which you bind firmly (intentionally). So its expiation is to feed ten needy people from the average of what you feed your own families, or to clothe them, or to free a slave. But whoever does not find (the means), then he must fast for three days. That is the expiation for your oaths when you have sworn (and then broken them). And guard your oaths. Thus does Allah make clear to you His verses so that you may be grateful (by obeying His commands).”

In this verse, the expiation (kaffarah) for oaths is mentioned, and acting upon any one of the four things for expiation is sufficient.

① Feeding ten needy poor people with average quality food.
② Giving clothes to ten needy poor people.
③ Freeing a slave (male or female).
④ Fasting for three consecutive days.