It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Pre-emption applies in slaves and in everything." Another narration has: "In a slave there is pre-emption, and in everything." (Da'if)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشفعة / 11602