It was narrated that Umayyah bin 'Abdullah bin Khalid bin Asid said to Ibn 'Umar:
"How can the Salah be shortened as Allah says: There is no sin on you if you shorten As-Salah (the prayer) if you are in fear?"  Ibn 'Umar said: "O son of my brother! The Messenger of Allah (ﷺ) came to us when we had gone astray and he taught us. One of the things that he taught us was that Allah, the Mighty and Sublime, has commanded us to pray two Rak'ahs when traveling."  An-Nisa' 4:101.