Sunan an-Nasa'i, Volume 3, Book 22, Hadith 2295 (DarusSalam) ⓘ
Mujahid narrated: That the Messenger of Allah fasted during Ramadan and broke his fast when traveling.
أَخْبَرَنِي هِلاَلُ بْنُ الْعَلاَءِ، قَالَ حَدَّثَنَا حُسَيْنٌ، قَالَ حَدَّثَنَا زُهَيْرٌ، قَالَ حَدَّثَنَا أَبُو إِسْحَاقَ، قَالَ أَخْبَرَنِي مُجَاهِدٌ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم صَامَ فِي شَهْرِ رَمَضَانَ وَأَفْطَرَ فِي السَّفَرِ .
also referenced under: Hadith 2293 (Reference) & Book 22, Hadith 204 (In-Book)