´It was narrated that Ibn Al-Simt said:` "I saw 'Umar bin Al-Khattab praying two rak'ahs in Dhul-Hulaifah and I asked him about that. He said: 'I am simply doing that which I saw the Messenger of Allah (ﷺ) doing.'"
Hadith ReferenceSunan an-Nasa'i / The Book of Shortening the Prayer When Traveling / Hadith: 1438
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم