Bukhari

Hadith Commentary: According to the majority of scholars, there is no objection in this matter, just as there is no objection to urinating while standing when there is an excuse preventing one from sitting. According to the narration of Muslim, the Prophet (sallallahu alayhi wa sallam) rebuked a person for drinking water while standing. The majority say that this prohibition is of a discouraging (tanzihi) nature, and it is better to drink water while sitting. Those who consider drinking water while standing to be disliked (makruh) also agree that drinking leftover ablution (wudu) water and likewise Zamzam water while standing is Sunnah.

And in the hadith of Ali, among its benefits is that when a scholar sees people avoiding something while he knows its permissibility, he should clarify the correct ruling for them, fearing that if the matter is prolonged, people may come to believe it is prohibited, etc. That is, from the hadith of Ali (radi Allahu anhu), this benefit becomes apparent: when a scholar sees that people are refraining from something that is permissible to consume, he should clarify its permissibility to dispel their incorrect assumptions; otherwise, one day the common people may come to regard it as completely forbidden.

Hadith Commentary:
(1)
In a narration from Anas radi Allahu anhu, it is reported that the Messenger of Allah sallallahu alayhi wa sallam forbade anyone from drinking while standing.
(Sunan Abi Dawud, Al-Ashribah, Hadith: 3717)
In light of this hadith, drinking while standing without a valid reason is not appropriate in any way.
Numerous ahadith have been reported on this subject; in fact, in some narrations it is mentioned that if someone forgetfully drinks water while standing, he should vomit it out.
(Sahih Muslim, Al-Ashribah, Hadith: 5279 (2026))

(2)
From these ahadith, it is evident that Islam encourages drinking while sitting in comfort, and this was also the regular practice of the Messenger of Allah sallallahu alayhi wa sallam, that he would drink water and the like while sitting calmly and peacefully. However, if there is a need, it is permissible to drink while standing, as the Messenger of Allah sallallahu alayhi wa sallam once visited the house of Kabshah radi Allahu anha, and there was a water-skin hanging in the house, so he sallallahu alayhi wa sallam drank water from it while standing.
(Jami‘ at-Tirmidhi, Al-Ashribah, Hadith: 1892)
But one should not make it a habit to drink while standing.

Benefits and Issues:
Benefit: There is a hadith in Jami' al-Tirmidhi which Imam Tirmidhi has declared authentic (sahih).
In it, Hazrat Kabshah radi Allahu anha narrated that the Messenger of Allah sallallahu alayhi wa sallam came to her house.
A water-skin was hanging in the house.
So he sallallahu alayhi wa sallam drank water from it while standing.
Then I cut off the part of the mouth of that water-skin (which the blessed mouth of the Prophet sallallahu alayhi wa sallam had touched) and kept it.
(Jami' al-Tirmidhi, Al-Ashriba, Hadith: 1892) From this hadith, it is also understood that although drinking directly from the mouth of a water-skin has been discouraged,
and the Prophet sallallahu alayhi wa sallam has prohibited it,
but this prohibition is not a prohibition of impermissibility (tahrimi).
Without making it a habit, it can be done when there is a need.
Just as is mentioned in the next hadith.
This action of the Prophet sallallahu alayhi wa sallam is a means of creating ease for the Ummah.
A similar incident is also narrated in Musnad Ahmad from Umm Sulaym radi Allahu anha.
(Musnad Ahmad: 376/6) Also, during the journey of Hajj, the Noble Prophet sallallahu alayhi wa sallam drank Zamzam while standing.
(Sahih al-Bukhari, Al-Hajj, Hadith: 1637)