Abu Salamah and Sa'id (may Allah have mercy on them both) both said that the Messenger of Allah (peace and blessings be upon him) said: "Pre-emption applies in whatever has not been divided; so when boundaries have been set, the right of pre-emption no longer remains."
Malik bin Anas (may Allah have mercy on him) narrated it thus in al-Muwatta as mursal, and it has also been narrated from him through other routes as connected (mawsul), mentioning Sayyiduna Abu Hurayrah (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشفعة / 11563