All praise is due to Allah, the Lord of all creation; may the peace and blessing be upon our noble Prophet Muhammad, his family, his Companions and all those who follow him precisely until the establishment of the Hour.
Many Muslims are unsure about the distance they must travel before they are considered travellers according to the Shariah. These rulings affect women too because they are required by the Shariah to travel with a male chaperone (mahram) on their journeys.
―Ibn ‘Uthaimeen, Al-Albani, Ibn Taymiyyah, Ibn Qudāmah And Those Scholars Who State A Journey Is According To The Practice And Custom Of A Land
Some of the scholars hold that there is no fixed limit of distance when considering whether one is travelling. They hold that a journey is whatever the people of a country consider to be a journey. So if it is called a journey in their customary practice, then it is treated as such: so they shorten the prayers as is the Sunnah, join the prayers and break the fast (if they choose). Shaikhul-Islām Ibn Taymiyyah stated: “The evidence supports those who say that the legislation allows the prayer to be shortened and the fast to be broken on whatever falls into the category of a journey — and they do not single out one type of journey to the exclusion of another.” 
Ibn ‘Uthaymeen was asked regarding the distance one needs to travel on a journey which requires one to shorten the prayers and whether it is permitted to combine instead of shortening the prayers. He answered, “The distance at which some of the scholars stated as a limit at which one can shorten the prayer is approximately 83km. Other scholars have considered the customary practice of the people [in a country] to be the measure which decides a journey even if that does not extend to 80km (or so). And that which the people (of a land) state regarding travel, “It is not a journey” then it is not a journey even if it reaches a 100km. And this was the preference of Shaikhul-Islam Ibn Taymiyyah (rahimahullah). That is because Allah (the Most High) and His Messenger (ﷺ) did not specify a particular distance at which one is permitted to shorten the prayers. Anas Ibn Mālik (may Allah be pleased with him) said, “Allah’s Messenger (ﷺ) would shorten the prayer to two rak’ahs at a distance of three miles or three farsakhs.”  The saying of Ibn Taymiyyah (may Allah’s mercy be upon him) is the closest to what is correct.
And when the custom (‘urf) of the people differs between themselves, then there is no harm if a person takes the saying of those scholars who set a limit (of approximately 80km) before one is considered a traveller — because that is the saying of some of the Imāms, Scholars and Jurists. So there is no harm in that (inshā’-Allāh). However, if the matter is clearly defined by the practice (‘urf) of the people, then it is returned back to that — and that is what is correct.”  Shaikh Al-Albāni also agreed with the position of Ibn Taymiyyah. Al-Albāni makes the added point that the ‘Urf of the people is the best measure as it agrees with the ease that Allah has prescribed for mankind in worship. 
Ibn ‘Uthaimeen Explains What Constitutes A Journey And How Long It Lasts
This part is extracted from Shaykh Ibn ‘Uthaimeen’s (rahimahullah) Sharh ‘Umatul-Ahkām (2/320-329):
The scholars have differed with respect to what is defined as the journey that allows one to shorten the prayers — so there are three sayings:
- A journey is every type of travel where a person leaves his land – and he stays away for as long as he wishes.
- A journey is that which is limited to a specified distance, beyond which one is regarded as a traveller.
- A journey is that which the custom of a land (i.e. its people) regard to be a journey, ‘Urf in Arabic.
Since we have already discussed the position of those scholars who hold that a journey that allows shortening of the prayers (and other allowances) is limited by distance travelled and length of stay, then here we shall discuss the third saying of the scholars, i.e. the ‘Urf of a people.
Firstly: Shortening the prayer for the traveller is a confirmed Sunnah (mu’akkadah) and to pray the full prayers on a journey is disliked (makrooh).
Secondly: If a traveller prays behind a person who is resident, then it is obligatory upon him to pray the full prayer and not to shorten even if he joined the prayer having missed the first two rak’ahs. This is due to the saying of the Prophet (ﷺ), “Whatever you have reached pray it (with the imām), and what you missed, complete it (after the imām makes tasleem).” (Bukhari, 635 and Muslim, 603). Ibn ‘Abbās was asked, “How should I pray when I am in Makkah when I am not praying behind the imām?” He replied, “Two rak’ahs as is the Sunnah of Abul-Qāsim (ﷺ).” (Muslim, 688)
Thirdly: The saying that a journey is defined by the normal practice of a people (‘urf) is the preferred position of Ibn Taymiyyah (Majmoo’ Al-Fatawa (24/135), Al-Muwaffaqud-Deen Ibn Qudāmah (Al-Mughni 2/152) and a group of other scholars. So whatever is known and called a journey by the people is a journey by definition. These scholars argue that to limit a journey to a specified distant requires a specific proof, and there is no proof. Following on from that: It is possible that a short distance is a journey if it takes a long time. For example, it is conceivable that we can leave from one place to another and it is a journey due to the distance travelled and the length of time one stays. So if we travelled to the town of Buraydah (38 km from ‘Unayzah), and we stayed there a day or two days, then we are travellers. But if we returned the same day, we are not travellers. That is because the distance is short, and the time spent there is small. However, if the distance was far and the time spent was small, then it is a journey. So, if we travelled to Riyadh by aeroplane (351 km from ‘Unayzah and 55 minutes by flight), and we returned the same day, then this is a journey — this is due to the fact the distance was far.
So this now becomes a journey defined by custom and practice (‘urf). Therefore a journey can be called a journey (where a person shortens his prayers) even though the distance travelled is small if the time spent on the journey is long. And a journey can be called a journey (where a person shortens his prayers) when the distance travelled is far even though it did not take a long time. This viewpoint from the aspect of reason and insight sits comfortably with one’s soul.
Fourthly: Does a person’s journey come to an end when he intends to remain at his destination alongside the fact that his intention of being a traveller remains? In this too the scholars have differed. Some of them said, “Wherever he intends to remain for four days or more, then his journey comes to an end and he must pray the full prayers. And he can no longer take the allowances and ease of a journey.” An-Nawawi (rahimahullah) mentioned in Al-Majmoo’ Sharhul-Muhadhdhab (4/321) over twenty sayings, each one conflicting with the other — and not one of them has a clear proof that brings tranquillity to the heart and upon which one can make a firm ruling. For this reason, we return to the origin of the affair, and that is: A traveller remains a traveller so long as he does not intend to settle in a place, or remain there indefinitely. “To settle in place” means that he leaves one lands for another land to live there permanently. “To remain there indefinitely” means he departs from his land and intends to stay in the new land indefinitely, and when he finds a suitable opportunity he will return to his land or to he will go to another land. So these two affairs stop him from being considered a traveller and taking the allowances and ease of a traveller.
If his journey is interrupted by a specific event such as work, or some days (of rest), then his being considered as a traveller does not come to an end. For example, a businessman stops in a land to purchase some goods or to sell some goods, but he does not know whether he will be purchasing (or selling) goods for a day or two days, or three days, or a month, two months, a year or two years — such a person takes the ruling of a traveller.
A person who leaves out on a journey to work (to another land or city), and he knows the exact length of his time away. For example, a person comes to a land to attend a conference (or a course) that lasts for three months, then such a person is considered a traveller who shortens his prayers because his journey has not come to an end.
Another example is a sick person who travels to a hospital (away from his land or city). He does not know when he will be fit enough to return, then it is allowed for him to shorten his prayers, even if he remains there for years on end. This is the position of the Hanbali scholars — and some of them reported ijmā’ (consensus) on the matter: That so long as a person remains on a journey that is restricted by a need that one has come to fulfil, he shorten his prayers until he returns to his land.
The issue of a journey being restricted (upon a person) by a time constraint is a matter of differing among the scholars. However, it is not necessary to dispute concerning this issue because he is just like the first example of the person who is constrained to remain at his destination due to work or a need (i.e. the businessman), or the second one who is constrained to remain at his destination due to the length of time (i.e. the three-month conference). Neither of them intended to discontinue their journey. So one was restricted from returning home due to completion of work (i.e. the businessman) and the other was restricted from returning home due to completion of a time period (i.e. three-month conference). There is no difference between the two — both are travellers.
Added to that: If a man intends to stay in place for four days, and another man intended to stay in a place for four days and ten minutes — so would we expect the first to shorten his prayers because he is a traveller but the second is not a traveller just because of the difference in their remaining at a destination is ten minutes?! How can that be?!
Therefore, that which the evidence points to, which leaves no discomfort in the soul is: So long as a person does not intend to stay in a place indefinitely or that he does not settle in a place to live permanently, then he is a traveller regardless if his remaining in a destination is due to a time restraint (as in the example of the person who attended a conference for three months) or whether his remaining in a destination is due to a need he wishes to fulfil (like the example of the businessman or the hospital patient). There is no difference between the two situations as far as the rulings of a traveller are concerned.
Fifthy: What is the reply to those who say that it is authentically reported that the Prophet (ﷺ) remained in Makkah for four days and that he only shortened his prayers for those four days? Then this hadeeth is actually a proof against those who use it to show that one can only shorten for four days once they have reached their destination. That is because the Messenger’s (ﷺ) arrival in Makkah on the 4th Dul-Hijjah was not something planned. The Prophet (ﷺ) knew that there were many other Muslims who had arrived to perform Hajj well before the 4th of Dhul-Hijjah. The season of Hajj begins from the 1st of Shawwāl and Allah has stated, “[Preparation for] Hajj is in the well-known months.” (2:197) And we know therefore that most pilgrims arrive before the 4th of Dhil-Hijjah. So did the Prophet (ﷺ) say to those who arrived before that they are to pray their prayers in full? If praying the prayers in full was an obligation then it would have been necessary for the Prophet (ﷺ) to convey that to them. So since he did not command them, then we can understand that the matter is not restrictive but open. So this hadeeth does not support the position of those who limit shortening of prayers to four days only, rather it is against them.
Also, it is known that the Prophet (ﷺ) stayed in Makkah for ten days as is proven by the hadeeth of Anas Ibn Mālik (radiyallahu ‘anhu) when he was asked how long they remained in Makkah in the year of the Farewell Hajj, he replied, “We stayed there for ten days.” (Bukhari, 1081 and Muslim, 694). They arrived on the 4th of Dhul-Hijjah and left for Madinah on the 14th Dhul-Hijjah.
It is proven also that the Prophet (ﷺ) stayed in Makkah for ten days at the Farewell Hajj. He stayed in Tabook for twenty days shortening the prayers (Abu Dawood, 1235). He stayed in Makkah for nineteen days in the year of the conquest shortening the prayers. So he stayed in different places for different lengths of times and he would always shorten the prayer. So it is not for us to restrict that which Allah has left unrestricted, because the religion provides ease and the spirit of the religion calls for ease and expanse for the worshippers — and it is not permitted for anyone to prohibit a person from that which Allah has allowed.
That which has been stated is the closest to the proofs and free from blind following and hardship upon the worshippers, It is the position of Ibn Taymiyyah (Majmoo’ Al-Fatawa 24/7, 15, 42, 44, 136, 141), Ibn Al-Qayyim (Zād al-Ma’ād 1/448) and Abdur-Rahmān As-Sa’dee (rahimahumullāh). All of them stating that there is no proof to restrict the length of time one can shorten the prayers whilst travelling.
Question 1: A man who leaves out [from his town] to shepherd his camels, is he a traveller?
Answer: He is a traveller because his heart is connected to his hometown and he knows that he has only left out for the welfare of his camels.
Question 2: What is the affair of the migrants who come here to work?
Answer: Those who are staying here, I think that they have the utmost desire to obtain a permit that allows them to stay indefinitely. So I would be very wary to say to them that you are travellers. They renew their permit to remain continually, and they would love to be given citizenship. So I cannot issue a verdict and say they are travellers. So I say they should pray the complete prayers, and it is not permitted for them to shorten. This also applies to the ambassadors. The origin is that they are resident in their respective embassies unless they are limited by time.
[End of notes from Ibn ‘Uthaimeen (rahimahullah)]
The well-known custom of the people is that when a person intends a journey, he gathers what he needs of provision and preparation (e.g. he collects food, clothing, puts petrol in the car, or purchases a train ticket, etc), then he leaves the limits of his town―so when he looks behind him, he sees the buildings and dwellings of his hometown― and he sees that he is out in the open (a motorway, or desert, or forest, etc)― so in that case he (or she) is considered a traveller.
This would explain why Anas Ibn Mālik (may Allah be pleased with him) said, “Allah’s Messenger (ﷺ) would shorten the prayer to two rak’ahs at a distance of three miles or three farsakhs.”  ―meaning that the Prophet (ﷺ) left his city intending a journey, and when he was out in the desert with the city of Madinah behind him, and the Prayer time had begun, he would pray shortened―even if that was only a short distance from Madinah.
And Allah knows best.
 Majmoo’ Al-Fatawa 24/106.
 Reported by Muslim, 691.
 Fatawa Arkān Al-Islām, p. 381.
 Reference audio.