Musnad Ahmad 27:1029

Yazid narrated to us, Yahya informed us, from Nafi’, that he informed him, saying: We came with Ibn Umar from Makkah, and we were traveling with him, and with him were Hafs ibn ‘Asim ibn ‘Umar and Musahiq ibn ‘Amr ibn Khidash. The sun set upon us, so one of them said: "The prayer." He did not speak to him. Then the other said to him: "The prayer." He did not speak to him. Nafi’ said: So I said to him: "The prayer." He said: "I saw the Messenger of Allah, peace and blessings of Allah be upon him, when he was hastened by travel, he would combine these two prayers." So I want to combine them. He said: So we traveled for miles, then he descended and prayed. Yahya said: Nafi’ narrated this hadith to me another time, and he said: We traveled until near a quarter of the night, then he descended and prayed.