Musnad Ahmad 33:882

Azhar ibn al-Qasim narrated to us, Salih ibn Abi al-Akhdar narrated to us, from al-Zuhri, from Abu Salamah, from Jabir: "The Messenger of Allah (peace and blessings of Allah be upon him) decreed the right of pre-emption (shuf'ah) as long as it has not been divided, or its boundaries have not been marked out."