Sunan Ibn Majah, Chapter: The Chapters on Hajj

"I heard the Prophet (saw) delivering a sermon in the Year of the Conquest (of Makkah), and he said: 'O people, Allah made Makkah sacred the day He created the heavens and the earth, and it is sacred until the Day of Resurrection. Its trees are not to be cut, its game is not to be disturbed, and its lost property is not to be taken except by one who will announce it.'Abbas said: 'Except for Idhkhir (a kind of fragrant grass), for it is (used) for houses and graves.' The messenger of Allah (saw) said: 'Except for Idhkhir.'"