"The Salah was enjoined two Rak'ahs at a time, then the Salah when traveling remained like that, but the Salah while resident was increased."
Sunan an-Nasa'i Book 5, Hadith 8
← Previous Hadith "Urwah told me that 'Aishah said: 'Allah enjoined the salah upon the Messenger of Allah (ﷺ), and the first thing that He enjoined was two Rak'ahs at a time, then it was made complete four Rak'ahs while in the state of residence but the prayer when traveling remained two Rak'ahs, as it was first enjoined.'"

Sunan an-Nasa'i Book 5, Hadith 7 Next Hadith → "The Salah was enjoined on the lips of the Prophet (ﷺ), four Rak'ahs while resident, and two while traveling, and one Rak'ah during times of fear."

Sunan an-Nasa'i Book 5, Hadith 9