Tirmidhi

1:
That is, both Hammad and ‘Asim have also narrated from Abu Wa’il, but Abu Wa’il has narrated from “Mughira ibn Shu’bah” radi Allahu anhu as well as from Hudhayfah.
This often happens that a narrator has narrated a hadith from two different narrators, so it is possible that Abu Wa’il heard it from both Companions.

2:
Because the narration of A‘mash is also found in the two Sahihs (Sahih al-Bukhari and Sahih Muslim), whereas the narration of ‘Asim is only in Ibn Majah, although that too is authentic.
(The matter is only about being “more authentic.”)

Benefits and Issues:
➊ It is understood that in cases of necessity, urinating while standing is permissible, provided there is no fear of splashing. Accordingly, in light of this hadith, it is narrated from Umar, Ali, Ibn Umar, and Zayd bin Thabit (radi Allahu anhum) that urinating while standing is permissible. However, the Sunnah is that a person should urinate while sitting, because it is narrated from Sayyidah Aishah (radi Allahu anha): "Whoever tells you that the Noble Prophet (sallallahu alayhi wa sallam) used to urinate while standing, do not confirm his statement, for the Prophet (sallallahu alayhi wa sallam) always used to urinate while sitting." [جامع الترمذي، الطهارة، باب ما جاء فى النهي عن البول قائما، حديث : 12، وسنن النسائي، الطهارة، حديث : 29] Imam Tirmidhi (rahimahullah) states that, regarding this issue, this narration is the most authentic. Furthermore, urinating while sitting provides greater concealment and a person is more protected from urine splashes. Nowadays, modern types of people, who have gone to extremes in imitating the West, urinate while standing in hotels and parks and feel pride in it, whereas imitating others in every matter is completely contrary to the hadith of the Messenger (sallallahu alayhi wa sallam). May Allah grant us the ability to act upon the Sunnah of the Prophet (sallallahu alayhi wa sallam) and protect us from imitating the English and non-Muslims.

➋ It is also understood that in certain situations, it is permissible to urinate near people.

Hadith Commentary: Benefits and Issues:
From this hadith, it is understood that if there is no place to sit and there is a need to urinate, then it is permissible to urinate while standing. This is because urinating while sitting is a sign of refinement and decency, and it is related to manners and etiquette. Therefore, occasionally, due to necessity, it is permissible to do so in this manner. The general habit of the Prophet (sallallahu alayhi wa sallam) was to go far away, but on this occasion, he did not go far, and for the sake of privacy, he had Hudhayfah (radi Allahu anhu) stand behind him.

18. Commentary:

➊ This narration is brief, which may lead to some misunderstandings; therefore, clarification has been attempted in the translation through parentheses. The correct account of the incident is that when the Messenger of Allah (sallallahu alayhi wa sallam) expressed the intention to urinate on a garbage heap, Hudhayfah (radi Allahu anhu), as usual, began to move away from him. However, since the Prophet only needed to urinate, in which there was no likelihood of sound or odor (especially in a standing position), he said to him: "O Hudhayfah! Provide me with a screen." So he stood close behind the Prophet, facing the other direction. (The phrase "near the heels" refers to general proximity, not literally standing heel to heel.) In this way, there was no possibility of looking towards the Prophet, and complete privacy was ensured.

➋ The general habit of the Prophet (sallallahu alayhi wa sallam) was to urinate while sitting, but in the mentioned incident, he urinated while standing. Various rational and textual explanations have been given for this, for example: to avoid the filth of the heap, because if he sat on the heap, his clothes or body could become soiled; or so that the stream of urine would fall farther away. In a sitting position, the urine would fall nearby and return towards the feet, and splashes could also occur; or due to difficulty in sitting because of pain in the knee, as is mentioned in a weak narration of al-Bayhaqi. [السنن الکبریٰ، للبیھقی : 101/1] Or for the treatment of back pain, as some physicians believed. In any case, in light of these explanations, the general opinion is that there must have been one of these reasons for the Prophet (sallallahu alayhi wa sallam) to urinate standing in this instance. However, the research is that none of these mentioned reasons are authentically established regarding the Prophet (sallallahu alayhi wa sallam), so in contrast, there is another opinion which Imam Nawawi (rahimahullah) and others have adopted, and that is that the Prophet urinated standing only to demonstrate permissibility, while his general habit was to urinate sitting. See: [صحیح مسلم، اطھارۃ، حدیث : 274، مع شرح النووي] Hafiz Ibn Hajar (rahimahullah) says regarding this, «وإلا ظھر أنه فعل ذلک لبیان الجواز……» "The clearer statement is that this action of the Prophet was only to demonstrate permissibility..." [فتح الباري : 430/1، طبع دارالسلام] Furthermore, Hafiz Ibn Hajar (rahimahullah) did not consider the transmitted explanations in this regard as authoritative. In any case, if a person, due to necessity or even occasionally without necessity, keeping in view the permissibility, urinates standing in order to act upon the Sunnah, then insha Allah it will be permissible. And Allah knows best.

➌ The purpose of the chapter is that if there is no fear of sound or odor, then only a screen is sufficient for urination; there is no need to go far away.