Musnad Abu Ya'la al-Mawsili 153:54

Muhammad ibn Ishaq al-Musayyibi narrated to us, Anas—meaning Ibn Iyad—narrated to us, from Yunus, from Ibn Shihab, that he said: Salim ibn Abdullah ibn Umar narrated to me that Abdullah ibn Umar said: I heard the Messenger of Allah (ﷺ) saying: "Whoever sells a slave, his wealth belongs to the one who sold him, unless the buyer stipulates [otherwise]. And whoever sells palm trees that have been pollinated, their fruit belongs to the one who sold them, unless the buyer stipulates [otherwise]."