Travel is one of the situations where the prayer is deliberately made lighter. It never stops — but on a journey a Muslim may shorten the longer prayers, and (in the view of most scholars) combine them in pairs. The Quran gives the permission:
"And when you travel throughout the land, there is no blame upon you for shortening the prayer, [especially] if you fear that those who disbelieve may disrupt [or attack] you. …"
— Quran 4:101 (Saheeh International)1
The verse mentions fear, and a companion once asked 'Umar why people still shortened now that they were safe. 'Umar had wondered the same, so he had asked the Prophet ﷺ, who answered:
"It is an act of charity which Allah has done to you, so accept His charity."
— Sahih Muslim 6862
Shortening (qasr)
'Aisha explained that prayer was first prescribed as two rak'ahs; "later the prayer in a journey was kept as it was but the prayers for non-travelers were completed."34 So on a journey:
| Prayer | At home | Travelling |
|---|---|---|
| Fajr | 2 | 2 |
| Dhuhr | 4 | 2 |
| Asr | 4 | 2 |
| Maghrib | 3 | 3 |
| Isha | 4 | 2 |
Only the four-rak'ah prayers are shortened; Fajr and Maghrib stay as they are.161718 Even when combining on a journey, the Prophet ﷺ prayed "three rak'at (of the Maghrib)" and then two of Isha.5
How strongly to take the concession is a point of difference:
If you pray behind a resident imam who prays four, pray four with him.161718
When does a journey count?
How far. The schools give a minimum distance:
In modern terms both are usually reckoned at around 80 km (about 50 miles), and some scholars hold that no fixed distance applies at all — whatever people customarily call travel counts.161718 Your local scholars will give the exact figure they follow. The concession begins once you have left your town or city behind, not while you are still packing at home: Anas prayed four rak'ahs of Dhuhr with the Prophet ﷺ in Madinah, and two of Asr once they reached Dhul-Hulayfah on the road.8161718
How long. The Prophet ﷺ shortened through ten days in Mecca on one journey6 and through nineteen days on another.7 The schools turned these reports into a working rule for someone who intends to settle at a place for a while:
If you are stuck somewhere without knowing when you will leave — waiting day to day — you remain a traveller.181617
Combining (jam')
On journeys the Prophet ﷺ often prayed two prayers together: "Allah's Messenger (ﷺ) used to offer these two prayers together on journeys i.e. the Maghrib and the 'Isha'."10 If he set out before midday he would delay Dhuhr and pray it with Asr.9 The pairs are always Dhuhr with Asr and Maghrib with Isha — never Fajr with anything, and never Asr with Maghrib.161718
Ibn 'Abbas also reported that the Prophet ﷺ once combined the prayers in Madinah "without being in a state of fear or in a state of journey," and explained that "he wanted that no one among his Ummah should be put to [unnecessary] hardship."11 Scholars differ on how far this reaches — most read it as permission for genuine need, such as heavy rain or illness, not as a habit — so ask a local scholar before relying on it at home.161718
Voluntary prayers on the road
Ibn 'Umar observed that on journeys the Prophet ﷺ "did not offer optional prayers during the journey"12 — meaning the regular sunnahs attached to the obligatory prayers. Yet the same Ibn 'Umar describes him praying voluntary prayers on his mount, facing wherever it was heading, gesturing for the bowing and prostration, "but not the compulsory prayer. He also used to pray witr on his (mount)."1314
That distinction is the one to carry onto a car, train or plane: voluntary prayer was prayed facing the direction of travel, while the obligatory prayers were not. For those, stand and face the qibla if you can; if you cannot, do what you are able to — "Pray while standing and if you can't, pray while sitting and if you cannot do even that, then pray lying on your side."15
In short
On a journey: pray Dhuhr, Asr and Isha as two rak'ahs, Fajr and Maghrib as usual; combine Dhuhr with Asr and Maghrib with Isha if your school permits it; and keep praying voluntary prayers however you are travelling. It is, in the Prophet's ﷺ words, a charity from God — accept it. For the other prayers that change with circumstances, see Beyond the Five.