Musnad Abu Ya'la al-Mawsili 153:13

And from al-Zuhri, Salim informed me, from his father, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever sells a slave who has wealth, then his wealth belongs to the seller, unless the buyer stipulates [otherwise]. And whoever sells date palms after they have been pollinated, then their fruit belongs to the seller, unless the buyer stipulates [otherwise]."