It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) sent for Sayyiduna Abu Taybah (may Allah be pleased with him), and he cupped him (performed hijamah). Then he (peace and blessings be upon him) asked him: "How much is your fixed levy (the daily amount you pay your master)?" He said: "Three sa'." So he (peace and blessings be upon him) had one sa' reduced from what he owed.
Hadith Referenceمسند أبي يعلى الموصلي / مسند جابر / 2057