Musannaf Ibn Abi Shayba 1:385

Sufyan ibn 'Uyaynah narrated to us, from 'Ubayd Allah ibn Abi Yazid, from Ibn 'Abbas, who said: I do not permit it for a person performing ghusl (full ritual bath) to bathe in the mosque, but for one drinking and one performing wudu (ablution), it is permissible and wholesome.