Musnad Abu Ya'la al-Mawsili 111:76

Narrated to us Abd al-A’la, narrated to us Mu’tamir, he said: I heard Layth, from Abu Fazara, from Yazid ibn al-Asamm, from Ibn Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I have not been commanded to construct/decorate mosques."