Muwatta Imam Malik Book of Jumu'a, Hadith 15

Malik said, "If the imam stops off on a journey in a town where jumua is obligatory and he gives a khutba and takes the jumua prayer for them, then the people of the town and any other people present do the jumua prayer with him."
Malik said, "If the imam gathers people for prayer while he is travelling in a town where the jumua prayer is not obligatory, then there is no jumua for him, nor for the people of the town, nor for anyone else who joins them for the prayer in congregation, and the people of the town and anyone else who is not travelling should complete the prayer."
Malik added, "A traveller does not have to do jumua "