Sunan an-Nasa'i, Hadith 2260 ⓘ
It was narrated from Jabir bin 'Abdullah that the Messenger of Allah said: "It is not righteousness to fast when traveling. Take to the concession which Allah, the mighty and sublime, has granted you, accept it."
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا وَكِيعٌ، قَالَ حَدَّثَنَا عَلِيُّ بْنُ الْمُبَارَكِ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ ثَوْبَانَ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، رضى الله عنهما عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ " لَيْسَ مِنَ الْبِرِّ الصِّيَامُ فِي السَّفَرِ عَلَيْكُمْ بِرُخْصَةِ اللَّهِ عَزَّ وَجَلَّ فَاقْبَلُوهَا " .
also referenced under: Book 22, Hadith 171 (In-Book) & Volume 3, Book 22, Hadith 2262 (DarusSalam)