Nasai

(1) The purpose of the title is absolutely clear: the milk of an animal whose entire or predominant diet consists of consuming filth is prohibited to drink.

(2) The reason for this prohibition is the same as has already been mentioned in the benefits and issues of the previous hadith: the effects of filth permeate into the milk of the animal that eats filth. And Allah knows best.

(3) From this blessed hadith, it is also understood that drinking water directly from the mouth of a waterskin is prohibited. The reason for this prohibition is that, in such a case, if there is any insect or any other harmful thing inside the waterskin, it may enter the mouth of the one drinking. For this reason, the Messenger of Allah (sallallahu alayhi wa sallam) forbade doing so. However, in a case of necessity, it may be drunk in this manner, but there is no general permission.

Explanation:
1:
Mujaththamah:
This refers to an animal upon which target practice is done until it dies.

Benefits and Issues:
➊
It is disliked (tanzihi) to drink directly from the mouth of a waterskin or by placing the mouth on a tap. The scholars have stated that this is only in the case when the waterskin is hanging; in such a situation, the permissibility of drinking directly is established. They have also transmitted the opinion that if the waterskin is hanging and cannot be taken down, or if no vessel is available, and it is also not possible to drink with the palm of the hand, then in this case there is no harm in drinking directly from the waterskin. (Fath al-Bari, Kitab al-Ashriba, Bab al-Mashrab min Famm al-Saqa’) Besides the possibility of the waterskin being damaged, it is also possible that some harmful thing may have entered the waterskin or the tap, and the one drinking may not be aware of it, and then he may suffer harm.

➋
The milk, meat, and riding of an animal that eats filth are all prohibited. If it is to be slaughtered, then it should first be kept tied up for at least three days. (Irwa’ al-Ghalil, narration: 2505)

➌
It is forbidden to kill a domesticated animal by targeting it (for sport), except if it becomes wild and falls under the ruling of game, then it is permissible.

Benefit:
In this hadith, one of the etiquettes of drinking water has been mentioned: that one should not breathe into the vessel while drinking water, rather, one should remove the vessel from the mouth and then breathe.