Sunan an-Nasa'i, Hadith 2305 ⓘ
It was narrated from 'Aishah that Hamzah bin 'Amr said: O Messenger of Allah, I am a man who fasts, so should I fast while traveling? He said: "If you wish then fast, and if you wish then do not fast."
أَخْبَرَنَا عَلِيُّ بْنُ الْحَسَنِ اللاَّنِيُّ، بِالْكُوفَةِ قَالَ حَدَّثَنَا عَبْدُ الرَّحِيمِ الرَّازِيُّ، عَنْ هِشَامٍ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، عَنْ حَمْزَةَ بْنِ عَمْرٍو، أَنَّهُ قَالَ يَا رَسُولَ اللَّهِ إِنِّي رَجُلٌ أَصُومُ أَفَأَصُومُ فِي السَّفَرِ قَالَ " إِنْ شِئْتَ فَصُمْ وَإِنْ شِئْتَ فَأَفْطِرْ " .
also referenced under: Book 22, Hadith 216 (In-Book) & Volume 3, Book 22, Hadith 2307 (DarusSalam)