Sunan Ibn Majah, Volume 2, Book 5, Hadith 1194 (DarusSalam) ⓘ
It was narrated that Ibn ‘Abbas and Ibn ‘Umar said: “The Messenger of Allah prescribed two Rak’ah of prayer when traveling; they are complete and are not shortened. And Witr when traveling is Sunnah.”
حَدَّثَنَا إِسْمَاعِيلُ بْنُ مُوسَى، حَدَّثَنَا شَرِيكٌ، عَنْ جَابِرٍ، عَنْ عَامِرٍ، عَنِ ابْنِ عَبَّاسٍ، وَابْنِ، عُمَرَ قَالاَ سَنَّ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ صَلاَةَ السَّفَرِ رَكْعَتَيْنِ وَهُمَا تَمَامٌ غَيْرُ قَصْرٍ وَالْوِتْرُ فِي السَّفَرِ سُنَّةٌ .
also referenced under: Hadith 1194 (Reference) & Book 5, Hadith 1250 (In-Book)