A traveller may shorten his salah as long as he is on a journey. Likewise if he stays in some place for business or some other affair, then he may shorten his salah as long as he is there, even for years. If the person intends to stay in a place for a certain amount of time then, according to Ibn al-Qayyim, he remains a traveller, regardless of whether he plans to stay there for a long or short time, as long as he does not plan to stay [i.e., reside and not return] in the place that he has travelled to. The scholars differ on this point. Summing up and giving his own opinion, Ibn al-Qayyim says: “The Messenger of Allah stayed in Tabuk for twenty days and during that time he shortened his salah and he did not say that one may not shorten his salah if he stays longer than that, although there is agreement that he did stay there for that period of time.”
In Sahih al-Bukhari, it is recorded that Ibn ‘Abbas said: “The Prophet stayed, during some of his journeys, for nineteen day and he prayed only two rak’at. If we stayed in a place for nineteen days, we would not pray the complete salah. However, if we stayed longer than that, we would perform the whole salah.” Ahmad states that ibn ‘Abbas was referring to the Prophet’s stay in Makkah at the time of its conquest when he said: “The Messenger of Allah stayed in Makkah for eighteen days during the time of the conquest as he had to go to Hunain and was not planning to stay there.” This is his interpretation of Ibn ‘Abbas’ statement. Others say that Ibn ‘Abbas was referring to the Prophet’s stay in Tabuk as Jabir ibn ‘Abdullah said: “The Messenger of Allah stayed in Tabuk for twenty days and performed qasr salah.” Imam Ahmad related this in his Musnad. Al-Miswar ibn Makhramah reports: “We stayed with Sa’d in some of the cities of ash-Sham [Syria] for forty days, and Sa’d would perform qasr while we would offer the whole salah.” Naf’i relates: “Ibn ‘Umar was in Azerbaijan for six months, as there was snow blocking the pass, and he would pray two rak’at.” Hafs ibn ‘Ubaidullah says: “Anas ibn Malik stayed in ash-Sham for two years and he prayed the salah of a traveller.” Anas relates: “The companions of the Prophet stayed in Ram Hurmuz for seven months and they shortened their salah.” Al-Hassan reports: “I stayed with ‘Abdurrahman ibn Samurah for two years in Kabul, and he shortened his salah but he did not combine the salah.” Ibrahim says: “We resided in Rai for a year or more and in Sijistan for two years… [and we prayed qasr]. This is the guidance of the Prophet and his companions, and this is the correct position.
Concerning other opinions which people follow Imam Ahmad say: “If a person intends to stay for four days, he has to offer the whole salah and he may offer qasr if his intention is for less than that. This is based on an interpretation of the reports from the Prophet and his companions [i.e., they never intended to stay for longer than that and would always say: ‘We will leave tomorrow,’ and so on]. This interpretation is obviously suspect. The Prophet conquered Makkah and stayed there to establish Islam, eradicate polytheism, and to guide the Arabs. It definitely goes, without saying, that such an objective does take more than a day or two to complete. Similarly, his stay in Tabuk was in preparation for the impending war and he knew that this might take longer than just four days. In the same way, Ibn ‘Umar’s stay in Azerbaijan for six months, and his praying qasr during the entire time was with the knowledge that it takes more than two or three days for such snow to melt and the pass to become traversable. The same is the case with Anas’ stay of two years in ash-Sham and his praying qasr and the companions’ stay in Ram Hurmuz for seven months while shortening their prayers. It is well known that activities like theirs, such as jihad and guarding, took more than four days.” The followers of Ahmad maintain: “If one is staying in a place for the purpose of jihad or due to imprisonment or sickness, then one may shorten one’s salah regardless of whether the person thinks that such a situation may last for a short time or a long time.” This is correct but there is no proof that such conditions have been stipulated in the Qur’an, Sunnah, ijma’ (consensus), or practice of the Prophet’s companions. They argued that such conditions are based on what is needed for the person to fulfil his need while remaining a traveller, and that is what is less than four days. His response to them was: ‘From where do you derive those conditions, while the Prophet sallallahu alehi wasallam stayed for more than four days, shortening his salah, in Makkah and Tabuk, and he did not mention to anyone anything about it and he never told them that he never intended to stay for more than four days, even though he knew that the people would [strictly] follow his actions concerning the salah. They surely followed him in his shortening of the salah, and he did not object to their praying qasr if they were to stay for more than four nights. This should be made clear as it is very important. Similarly, the companions (as-sahabah) followed him in that and he did not say anything [in objection] to those who prayed with him.”
Malik and ash-Shaf’i say: “If one intends to stay for more than four days, he should perform the whole salah, and if he intends to stay for less than that, he is to offer qasr.”
Abu Hanifah holds: “If one intends to stay for fifteen days, he should do the qasr. If he intends to stay for less than that, he should not shorten the salah.” This is also the opinion of al-Laith ibn Sa’d, and it has also been related from three companions: ‘Umar, ibn ‘Umar, and Ibn ‘Abbas.
Sa’id ibn al-Musayyab is of the opinion that: “If you stay for four days, you pray four rak’at.” A statement similar to that of Abu Hanifah’s has also been related from him. ‘Ali ibn Abi Talib says that if one stays for ten days, he is to perform the whole salah, and the same has been related from Ibn ‘Abbas.
Al-Hassan says: “One who does not get to his destination or (city of residence) may shorten salah.”
‘Aishah says: “One who does not put down his provision is to shorten the salah.”
The four imams agree that if one has some need to take care of and always has the intention of leaving the next day, then he may shorten his salah for as long as he is in that state. However, according to one statement of ash-Shaf’i, he may do so only for seventeen or eighteen days and he is not to shorten his salah after that time. Ibn al-Munzhir states in his Ishraf: “The people of knowledge are in agreement that a traveller may perform qasr as long as he does not intend to stay in a place, even though he stays there for years.”