question #3 Sahih Muslim 685b, Book 6, Hadith 2 : How does the practice of prayer differ between when one is at home and when one is traveling?

‘A’isha, the wife of the Messenger of Allah (ﷺ), said Allah prescribed the prayer as two rak’ahs, then it was completed (to four rak’ahs) at the place of residence, but was retained in the same position in journey as it was first made obligatory.