Sunan an-Nasa'i #2292 · The Book of Fasting

Sunan an-Nasa'iIt was narrated that Al-'Awwam bin Hawshab said
Sunan an-Nasa'i · Book 22 · The Book of Fasting
Sunan an-Nasa'i · كتاب 22 · كتاب الصيام
"I said to Mujahid: 'What about fasting while traveling?' He said: 'The Messenger of Allah used to fast (sometimes) and not fast (sometimes)
أَخْبَرَنَا حُمَيْدُ بْنُ مَسْعَدَةَ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الْعَوَّامِ بْنِ حَوْشَبٍ، قَالَ قُلْتُ لِمُجَاهِدٍ الصَّوْمُ فِي السَّفَرِ قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُ وَيُفْطِرُ ‏.‏
Reference : Sunan an-Nasa'i 2292In-book reference : Book 22, Hadith 203