Musannaf Ibn Abi Shayba 1:386

386. Isa ibn Yunus narrated to us, from Ubayd Allah ibn Abd al-Rahman ibn Mawhab, from Salih ibn Muslim al-Laythi, who said: I saw Ibn Jubayr ibn Mut'im in the mosque. He cleared away the pebbles, then he performed his entire ablution in the mosque.