Muwatta Malik Book 9, Hadith 11
Yahya related to me from Malik from Yahya ibn Said that he said
to Salim ibn Abdullah, "What is the latest you have seen your father
delay maghrib while on a journey?" and Salim replied, "One time the
sun set when we were at Dhat al-Jaysh and he prayed maghrib at al-
Aqiq."
Yahya related to me from Malik from Salih ibn Kaysan from Urwa ibn az-Zubayr that A'isha, the wife of the Prophet, may Allah bless him and grant him peace, said, "The prayer was prescribed as two rakas, both when settled and when travelling. Then the travelling prayer was kept as it was, and an increase was made in the prayer when settled. "
Yahya related to me from Malik from Nafi that Abdullah ibn Umar, shortened the prayer when he left for hajj or umra at Dhu'l Hulayfa.