Bukhari

Explanation:
It is Sunnah to begin with the right side in ablution (wudu) and ritual bath (ghusl), and this method is Sunnah in other actions as well.

Hadith Commentary:
1.
In the Arabic language, "tayammum" has several meanings. For example: to begin from the right side, to take something with the right hand, to seek blessing, and to take an oath, etc. Imam Bukhari rahimahullah has specified the meaning of "tayammum" in the aforementioned hadith of Umm Atiyyah radi Allahu anha as beginning from the right side. This word is found in the narration of Sayyidah Aisha radi Allahu anha, that the Messenger of Allah sallallahu alayhi wa sallam liked tayammum in every matter. (Fath al-Bari: 1/358) It is well known regarding Imam Bukhari’s method of titling that when he finds difficulty in deducing evidence for a particular issue under discussion, he expands the title by including something similar, which makes it easier to derive the intended ruling. Here too, when he found a scarcity of hadiths regarding beginning ablution (wudu) from the right side, he included the issue of ritual bath (ghusl) along with ablution, so that the issue of beginning from the right side in ablution becomes clear from the issue of tayammum in ghusl, because the ruling is the same in both ghusl and ablution. Thus, when it is required to begin from the right side in the ablution of the deceased during ghusl, then it is even more appropriate to observe this in the ablution for prayer.

2.
Regarding the instructions that the Messenger of Allah sallallahu alayhi wa sallam gave about giving his daughter a ritual bath (ghusl), there are two points:
(1)
To begin from the right side.
(2)
To begin from the parts of ablution (wudu).
The only way to act upon both these points simultaneously is to begin the ritual bath from the limbs of ablution in such a way that first the right hand of the deceased is washed, then the left hand; similarly, when it comes to washing the feet, first the right foot, then the left foot is washed. After this, the entire body is given a ritual bath.

3.
Imam Bukhari rahimahullah has mentioned the hadith of Aisha radi Allahu anha in the second position, even though it contains the word "tahur" which is a strong proof regarding beginning from the right side during ablution. However, he did not base his chapter heading on this hadith because the words "tayammum" and "tahur" in this hadith are not explicit for the intended purpose due to their shared and ambiguous meanings. As we have mentioned earlier, the word "tayammum" is shared in the meanings of beginning from the right side, taking an oath, seeking blessing, and taking with the right hand. Similarly, there is ambiguity in the word "tahur" as to whether it refers to the purification of the body or the clothes, and whether it refers to ritual bath (ghusl) or ablution (wudu). For these reasons, Imam Bukhari rahimahullah gave the hadith of Aisha radi Allahu anha the second position and established the issue under discussion from the hadith of Umm Atiyyah radi Allahu anha by giving it the first position.

4.
The rule regarding choosing the right side is that matters related to honor and respect, and to adornment and beautification, should be started from the right side. For example: wearing clothes, putting on socks, entering the mosque, using the tooth-stick (miswak), applying kohl, cutting nails, trimming the mustache, combing the hair, removing armpit hair, shaving the head, turning for salam in prayer, washing the limbs of purification, exiting the toilet, eating, drinking, shaking hands, kissing the Black Stone (Hajar al-Aswad), etc. And in matters contrary to these, the left side should be chosen. For example: entering the toilet, exiting the mosque, performing istinja (cleansing after relieving oneself), cleaning the nose, removing clothes or socks or stockings, etc. Also, there are some limbs of ablution in which the right or left is not considered, rather they are to be washed at once, such as the hands, ears, cheeks, etc. (Umdat al-Qari: 2/472)

5.
In some narrations, it is mentioned that the Messenger of Allah sallallahu alayhi wa sallam would give preference to the right side as much as possible. (Sahih al-Bukhari, Salat, Hadith: 426) This means that if there is any hindrance in choosing the right side, then there is no harm in choosing the left side. (Fath al-Bari: 1/354)