It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Pre-emption applies in whatever has not been divided; when boundaries have been set, there is no pre-emption."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشفعة / 11565