Musannaf Ibn Abi Shayba 3:2322

Waki’ narrated to us, Abu Isra’il narrated from Musa al-Juhani, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "This nation—or he said: my nation—will continue to be in goodness as long as they do not adopt in their mosques decorations like the decorations of the Christians."