Salim b. 'Abdullah (b. 'Umar) reported on the authority of his father that Allah's Messenger (ﷺ) observed the prayer of a traveller, i. e. two rak'ahs in Mina, and other places; so did Abu Bakr and 'Umar, and 'Uthman too observed two rak'ahs at the beginning of his caliphate, but he then completed four.
Reference | : Sahih Muslim 694a |
In-book reference | : Book 6, Hadith 21 |
USC-MSA web (English) reference | : Book 4, Hadith 1477 |
(deprecated numbering scheme) |