Shortening the prayer (qasr)
Allah says there is no blame on believers for shortening the prayer when they travel (Quran 4:101). The verse mentions fear, but when Umar asked the Prophet ﷺ about shortening the prayer in safety, he said it is a charity that Allah has given, so accept His charity (Sahih Muslim 686). Aisha, may Allah be pleased with her, reported that the prayer was first made two rak'ahs, and the prayer of the traveller stayed at two (Sahih al-Bukhari 350). The Prophet ﷺ prayed two rak'ahs on his journey from Madinah to Makkah (Sahih al-Bukhari 1081).
Only the prayers with four rak'ahs are shortened. They are Dhuhr, Asr and Isha, and each becomes two rak'ahs. Fajr stays at two and Maghrib stays at three.
Scholars differ on the status of shortening. The Hanafi school says it is required for the traveller. The Maliki school calls it a confirmed sunnah. The Shafi'i and Hanbali schools see it as a concession, and they say it is better to use it.