أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا ابْنُ عَوْنٍ، عَنْ مُحَمَّدٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كُنَّا نَسِيرُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم بَيْنَ مَكَّةَ وَالْمَدِينَةِ لاَ نَخَافُ إِلاَّ اللَّهَ عَزَّ وَجَلَّ نُصَلِّي رَكْعَتَيْنِ ‏.‏

It was narrated that Ibn 'Abbas said: "We used to travel with the Messenger of Allah (PBUH) between Makkah and Al-Madinah, fearing nothing but Allah, the Mighty and Sublime, and praying two rak'ahs." Translation Not Available

Book Ref: Sunan An Nisai Book 15 Hadith 1436
Web Ref:  Sunan An Nisai Vol 2 Book 15 Hadith 1437