Bukhari

Hadith Commentary:
In the earlier ahadith, there is a prohibition for a woman to travel for three days without a mahram (a male relative whom she cannot marry), whereas in this hadith, the duration mentioned is one day and one night.
By "day," Imam Bukhari rahimahullah intends to clarify the minimum and maximum limits of the term "journey" (safar), that is, the duration of one day and one night is considered the initial part of a legal journey (shar‘i safar), and a journey of three days is considered its final part.
As for anything longer than this, it has already been explained that, according to the Ahl al-Hadith, performing qasr (shortening the prayers) is a Sunnah, not an obligation or a compulsory act.
However, it is certainly true that qasr is a charity (sadaqah) from Allah, and it is most appropriate to accept it.

Hadith Commentary:
(1)
From this hadith, Imam Bukhari rahimahullah has established that for shortening the prayer (qasr), the minimum distance must be that which can be covered in one day and one night. In summary, there is no explicit verbal narration from the Messenger of Allah sallallahu alayhi wa sallam regarding this matter from which the specific distance for shortening the prayer could be determined. However, Anas radi Allahu anhu, who accompanied the Messenger of Allah sallallahu alayhi wa sallam as a special servant during both travel and residence, deduced from one of his actions that the prayer may be shortened at a minimum distance of nine miles. Accordingly, his student Yahya bin Yazid asked about the required distance for shortening the prayer, and Anas radi Allahu anhu replied that when the Messenger of Allah sallallahu alayhi wa sallam traveled three miles or three farsakh, he would shorten the prayer.
(Sahih Muslim, Salat al-Musafirin wa Qasruha, Hadith: 1583(691))
In the narration, the hesitation regarding the specification of the journey is attributed to Shu’bah, the narrator.

(2)
It should be noted that in the narration, taking “three farsakh” instead of “three miles” is more plausible, because miles are also included in this, as one farsakh is equal to three miles. This means that if the distance is nine miles, then after leaving the boundary of one’s city or village, the prayer may be shortened. Some scholars are of the opinion that the shortening should begin after covering such a distance. The narration does not mention the end point of the journey, and this interpretation of the narration is not correct because the questioner asked Anas radi Allahu anhu specifically about the distance required for the permissibility of shortening the prayer, and he was answered accordingly. After this, to assume that, as a matter of fact, it is not established that the Messenger of Allah sallallahu alayhi wa sallam ever undertook a journey of only this distance, is nothing more than a subtle point, because Anas, the special servant of the Messenger of Allah sallallahu alayhi wa sallam, understood the question of the questioner and answered it accordingly, which we should accept.
And Allah knows best.

(3)
The corroboration (mutaba’ah) of Yahya bin Abi Kathir has been narrated by Imam Ahmad rahimahullah with his connected chain. The narration of Suhail has been narrated by Ibn Khuzaymah, and the narration of Imam Malik has been narrated by Imam Muslim with a connected chain.
(Fath al-Bari: 2/734)

1723. Commentary: The meaning of the hadith is absolutely clear that no woman may undertake even a one-night journey without a mahram, even if it is a blessed journey such as Hajj. If, hypothetically, a woman does not have any mahram available to her, then she falls outside the necessary capability (istita‘ah) for Hajj, and Hajj will not be obligatory upon her. For details, see (Nayl al-Awtar: 4/324). However, some scholars, under specific circumstances and with particular conditions, permit a woman to perform Hajj without a mahram. For example, an elderly woman whose youth has passed may undertake the journey of Hajj with a trustworthy caravan in which there are also reliable women.

➋ A mahram is a person with whom marriage is permanently forbidden for a woman, such as father, grandfather, paternal uncle, maternal uncle, nephew, son, father-in-law, etc.

Benefits and Issues:

➊
A woman should not undertake a long journey without her husband or a mahram (unmarriageable kin).

➋
A short journey, such as going to a nearby village or from one neighborhood of a city to another, is permissible without a mahram provided there is no risk of any kind of temptation or mischief; however, it is still better that a mahram accompanies her.

➌
The purpose of this restriction is to safeguard the chastity, purity, honor, and dignity of the woman.

➍
By mahram is meant such a man with whom marriage is permanently forbidden for the woman, whether this relationship is by blood, by breastfeeding (rada‘ah), or by marriage ties (musaharah).
The details of these relationships have already been explained in Kitab al-Nikah, Chapter 34.

Hadith Authentication:
[وأخرجه مسلم 1339/421، من حديث ما لك به، وعلقه البخاري 1088، وفي رواية يحيى بن يحيى : ”تسافر“]

Jurisprudential Understanding:
➊ It is not permissible for any woman to undertake a long journey from her locality to another place, which is considered a journey according to the Shariah or customary practice, without a mahram (unmarriageable male relative). According to the preferred opinion, the journey begins once she leaves her locality, provided that the destination is at a distance of eleven miles or more from her.
➋ From the opposite implication (mafhum mukhalafah) of this hadith, it is understood that for a journey less than a day and night, a woman may, in case of necessity and in a state of safety and security, travel without a mahram. See [التمهيد 52/21]
➌ It is narrated from Sayyiduna Adi bin Hatim al-Tai radi Allahu anhu that the Messenger of Allah sallallahu alayhi wa sallam said: [فإني لا أخاف عليكم الفاقة فإن الله ناصر كم و معطيكم حتى تسير الظعينة فيما بين يثرب والحيرة أو أكثر، ما يخاف علٰى مطيتها السرق.]
I do not fear poverty for you, for Allah will help you and grant you (abundant provision) until a woman riding on a camel litter will travel between Yathrib (Madinah) and Hira (a distant city) or even farther, and she will have no fear of her animal being stolen. [سنن الترمذي:2953 ب وقال: ”هذا حديث حسن غريب“ وسندہ حسن لذاته وصححه ابن حبان، الموار:2279]
● This woman will travel from Hira and come to the House of Allah and perform tawaf (circumambulation). [صحيح بخاري:3595]
◄ From this hadith, it is understood that if there is a legitimate (shar‘i) excuse, a woman may travel alone for Hajj and similar acts. Regarding a woman who has never performed Hajj, Hasan bin Abi al-Hasan (al-Basri) rahimahullah used to permit her to perform Hajj with another woman who has a mahram with her. [مصنف ابن ابي شيبه 4/4 ح 15164 وسنده صحيح]
● According to Imam al-Shafi‘i rahimahullah, if there are trustworthy women with her, then she may travel with them for Hajj. See [كتاب الام ج 2ص 117، باب حج المرأة والعبد]

Benefit:
It is established from this hadith that a woman should not travel without a mahram. The restriction of "three days" is an agreed-upon restriction, and especially in the present era, it is possible to travel several thousand kilometers within three days. Whatever is considered a journey, whether it is short or long, a woman cannot travel in it without a mahram.