What is the ruling if a person starts the Jumu'ah prayer but later discovers another Jumu'ah has already been established in the city?
General Chapter
Al-Mughni
Book of Friday Prayer
Primary text
If one initiates the Jumu'ah prayer and later discovers that Jumu'ah has already been established in the city, their prayer is invalidated, and they must restart with the Dhuhr prayer. This is because it becomes evident that they initiated the prayer at a time when Jumu'ah was not permissible for them, similar to starting after the time for Asr has entered.
Supporting text
The view of the Qadi suggests it is recommended to complete it as Dhuhr, analogizing it to a latecomer who misses the bulk of the prayer or when the congregation disperses during the Jumu'ah prayer before completion.