Abu Dawud Book 2, Hadith Number 1208.

Chapter : On the combination of two prayers at a time.

Narated By Abdullah ibn Umar : Abdullah ibn Waqid said: The mu’adhdhin of Ibn Umar said: prayer (i.e. the time of prayer has come). He said: Go ahead. He then alighted before the disappearance. He then offered the night prayer. He then said: When the Apostle of Allah (PBUH) was in a hurry about something, he would do as I did. Then he travelled and covered a distance of three days’ journey on the day.

Abu Dawud siad: A simmilar tradition has been transmitted by Ibn Ja’far from Nafi’ with the same chain.