Sunan Abi Dawud Book 2, Hadith 99
The earth has been made for me purifying and as a mosque (place for prayer).
The Jews came to the Prophet (May peace be upon him) and he was sitting in the mosque among his Companions. They said: O Abu al-Qasim, a man and a woman have committed adultery.
AbuSalih al-Ghifari reported: Ali (once) passed by Babylon during his travels. The mu'adhdhin (the person who calls for prayer) came to him to call for the afternoon prayer. When he passed by that place, he commanded to announce for the prayer. After finishing the prayer he said: My affectionate friend (i.e. the Prophet) prohibited me to say prayer in the graveyard. He also forbade me to offer prayer in Babylon because it is accursed.