ENOfficial
It was narrated that Al-'Awwam bin Hawshab said: "I said to Mujahid: 'What about fasting while traveling?' He said: 'The Messenger of Allah (ﷺ) used to fast (sometimes) and not fast (sometimes)."'
Source: sunnah.com
Other translations
Arabic
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 .
sunnah.com