It is narrated from Abu Ma'bad that Ibn Abbas (may Allah be pleased with him) used to buy dates from his slave before they were eaten, and he did not consider it usury between himself and his slave.
Hadith Referenceمسند الإمام الشافعي / كتاب البيوع / 1425
Hadith Takhrijاسناده صحيح: اخرجه البيهقي : 302/5 - وفى المعرفة السنن والآثار له (3398)۔ وعبدالزاق (14378)۔ و ابن ابي شيبة (20034)، (20035)۔