What is the ruling on prayer when a resident leads other travelers and then appoints a substitute?
Chapter on the Traveler's Prayer
Al-Mughni
Book of Prayer
Primary text
If travelers praying behind a resident experience an event where the resident appoints another traveler as a substitute imam, the travelers must still complete the prayer because they originally joined a resident. If the substitute appointed is a resident, completing the prayer is also mandatory.
Supporting text
If travelers praying behind a traveler experience an event where the imam appoints a replacement traveler, the group may shorten the prayer because they did not join a resident. If the original imam who was traveling appoints a resident substitute, the group must complete the prayer. The original imam, having not followed a resident, is permitted to pray the traveler's prayer (two rak'ahs).