Ruling 1683 — Fasting (Ṣawm)

A traveller must not fast if his obligation on a journey is to perform the four-unit (rakʿah) prayers as two rakʿahs [i.e. in qaṣr form]. A traveller who performs his prayer in its complete (tamām) form – such as someone whose work is travelling or whose journey is sinful – must fast on his journey.