What prayer ruling applies to a person passing through a town without intending to reside there?
Chapter on Facing the Qiblah
Al-Mughni
Book of Prayer
Primary text
If one enters a town merely passing through, without intending to reside or intending to depart without reaching the period requiring full prayer, one continues to perform the shortened traveler's prayer (Salat al-Qasr) as long as one is moving. Upon stopping (Nuzul), one prays facing the Qibla and builds upon whatever part of the prayer has already been performed, similar to the ruling for a fearful person who becomes secure during their prayer.
Supporting text
If one begins prayer while settled and intending to ride, they must complete the prayer first and then mount. An alternative view suggests one may mount during the prayer and complete it facing the direction of travel, similar to the secure person who becomes fearful during prayer.