What is the definition of "travel" (safar) according to Islamic Law (fiqh)?

In a Nutshell: There are different scholarly opinions on the distance that constitutes travel, ranging from 1 day to 3 days of journey. Some scholars define travel by experience rather than distance. Leaving inhabited areas on a journey with provisions. Scholars also differed on how long someone remains a traveler after arriving at a destination before becoming a resident. Opinions range from 4 days to having no time limit as long as intending to return home. Travel has implications in Islamic law - a traveler may shorten prayers from 4 units to 2 units, combine prayers, and break fast during Ramadan. The differences of scholarly opinion demonstrate the complexity of deriving specific regulations for defining travel, with evidence existing for multiple views. Key principles are travel involves leaving one's home/city, psychologically preparing for a journey, and intending to return home eventually. Introduction Travel (safar) has an important implication in Islamic law. A traveler may shorten prayers (qasr), combine them (jam‘), and break fast during Ramadan (fiṭr). The Quran explicitly allows shortening prayers during travel: "And if you travel in the land, there is no sin on you that you shorten your prayers if you fear that the unbelievers may harm you.” [Sūra al-Nisāʾ:101] The verse mentions ‘fear’ as a condition, but it is no longer required. When Umar ibn al-Khattab was asked how shortening was allowed without fear, he replied that the Prophet said: “This is a charity that Allah has given to you, so accept His charity.” [Muslim] Allah has lifted the condition and allows shortening even without fear. The Prophet (saw) would shorten every four-unit prayer to two units when traveling. He never prayed full four-unit prayers. [1] There is consensus that a legitimate traveler may shorten prayers. [2] The question is: when does one legally become a ‘traveler’? This answer will: 1) Discuss opinions on the distance constituting ‘travel’ 2) Discuss time duration before a traveler becomes a resident. Opinions on Distance Constituting 'Travel' Ibn al-Mundhir mentioned close to 20 opinions on the distance. We will focus on the four most famous: First Opinion: A three-day journey The distance a traveler on a camel would cover in three days. This is the view of Ibn Mas‘ūd, Kufa scholars like al-Sha‘bī and al-Nakha‘ī, and the standard Ḥanafī position. They based this on the hadith where the Prophet (saw) said: “It is not allowed for a woman who believes in Allah and the Last Day to travel a distance of three days without a mahram.” [Muslim] They reasoned the Prophet called three days' distance a ‘travel’. Another evidence was the hadith allowing a traveler to wipe socks for three days. They reasoned anyone traveling less than three days would not qualify and so cannot wipe socks or shorten prayers. [3] Second Opinion: A two-day journey The famous view of Ḥanbalīs, Shāfiʿīs and Mālikīs. Also reported from Ibn ‘Abbās, Ibn ‘Umar, al-Zuhrī and others. Their evidence is the hadith: “It is not allowed for a woman to travel a distance of two days without a mahram.” [Muslim] Also, Ibn ‘Umar would shorten after traveling two days. [Malik’s Muwaṭṭa] Third Opinion: A one-day journey Imam al-Bukhārī’s explicit view. Also a second opinion in the three schools above. Al-Awzāʿī said this was the majority opinion. Al-Shanqīṭī held this view. They cited the hadith: “It is not allowed for a woman to travel a distance of one day without a mahram.” [Bukhārī] Bukhārī commented this shows the Prophet considered one day's travel to be ‘travel.’ Ibn Abbās said shorten prayers when traveling a full day, but not for lesser distances like Mina. [Abd al-Razzāq] Fourth Opinion: Not defined by distance but by experience The view of Ibn Ḥazm, Ibn Qudamah, Ibn Taymiyya, Ibn al-Qayyim, al-Ṣanʿānī, and others. Interpreted as Ibn Mas‘ūd and ‘Uthmān’s view. They say no scriptural evidence defines ‘travel’. Ibn Taymiyya said demarcating a distance has no basis in Quran, Sunnah, language, or intellect. ‘Travel’ is an experience, not just distance. He said earlier generations did not measure distances in miles or farasikh. A person might leave home for two days to collect firewood and be a traveler due to preparing provisions and bags, while another traveling further might not be a traveler if returning the same day without preparation. Ibn Taymiyya said ‘travel’ in Arabic indicates ‘exposing’ oneself to the wilderness by leaving inhabited areas. Opinions on duration for a traveler to be a resident Scholars also differed on the time duration required for a traveler to become a resident in his destination. The opinions: First Opinion: 4 days - The traveler may shorten prayers for 4 days after arriving at the destination. This was the standard view of Imam Abu Hanifa and Sufyan al-Thawri. They based this on the hadith allowing wiping socks for 3 days and nights - the 4th day is for wiping, so prayers are shortened for the first 4 days. [Muslim] Second Opinion: 15 days - The famous view of Imam Malik, Ahmad, and al-Shafi’i. Their evidence includes: Abdullah ibn Umar would reside in Mecca for 4 months but would continue shortening prayers. [Muwatta] Ibn Abbas said a traveler may shorten until he prays one Friday prayer in his destination. They said the longest stay before Friday is 15 days. Third Opinion: No limit - As long as someone intends to return home, he remains a traveler. The view of al-Thawri, Ibn al-Mubarak, al-Awza‘i, Abu Thawr and many others. Was also attributed to Ahmad. Their evidence: Hadith of Fatima bint Asad visiting the Prophet (saw) in Medina while residing there - he still told her to shorten prayers. [Abu Dawud] No authentic report of Companions ceasing to shorten after some days in a destination. Conclusion This summarizes the main opinions on when one legally becomes a traveler, and when a traveler becomes a resident. There are other minority views not covered here. The differences of opinion show the complexity of deriving specific regulations for this issue. [1] Ibn Taymiyya, Majmūʾ al-Fatāwā, 24/8. [2] Ibn Hubayra, al-Ifṣāḥ, 2/55 [3] Muslim