It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) sent for Abu Taybah, who cupped him (peace and blessings be upon him), and he (peace and blessings be upon him) remitted half a sa', or more, of his levy (kharaj).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12532