Hadithcore
Musnad Ahmad 2064
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It was narrated that Ibn ‘Abbas said:

The Messenger of Allah (ﷺ) enjoined prayer when travelling and not travelling. Just as (nafl) prayers are offered when not travelling, before and after (the obligatory prayer), they should also be offered when travelling, before and after (the obligatory prayer).

References1 variant
Arabic/English book
Book 25, Hadith 2064