The statement is "True".
If you see the early history of Islam and look at the mosques which were built during the lifetime of the founder of Islam, one can hardly find any decorated mosques or his saying about decorating mosques like we see in the contemporary times, rather he is reported to have said that when people's practical deeds weaken, they start decorating their mosques, and at another place he said that the decoration of a Muslim mosque is due to its worshipers and not physical beauty.