Sunan an-Nasa'i, Book 22, Hadith 193 (In-Book) ⓘ
It was narrated that Ghalian said: "I went out with Abu Qilabah on a journey and he brought some food. I said: 'I am fasting.' He said: 'The Messenger of Allah went out on a journey and brought some food, and said to a man: Come and eat. He said: I am fasting. He said: Allah has waived for the traveler half of the prayer and fasting when traveling, so come and eat. So I came close and ate."'
أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، قَالَ أَنْبَأَنَا إِسْرَائِيلُ، عَنْ مُوسَى، - هُوَ ابْنُ أَبِي عَائِشَةَ - عَنْ غَيْلاَنَ، قَالَ خَرَجْتُ مَعَ أَبِي قِلاَبَةَ فِي سَفَرٍ فَقَرَّبَ طَعَامًا فَقُلْتُ إِنِّي صَائِمٌ . فَقَالَ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم خَرَجَ فِي سَفَرٍ فَقَرَّبَ طَعَامًا فَقَالَ لِرَجُلٍ " ادْنُ فَاطْعَمْ " . قَالَ إِنِّي صَائِمٌ . قَالَ " إِنَّ اللَّهَ وَضَعَ عَنِ الْمُسَافِرِ نِصْفَ الصَّلاَةِ وَالصِّيَامَ فِي السَّفَرِ " . فَادْنُ فَاطْعَمْ فَدَنَوْتُ فَطَعِمْتُ .
also referenced under: Hadith 2282 (Reference) & Volume 3, Book 22, Hadith 2284 (DarusSalam)