Sa'id bin Abi Sa'id al-Maqburi (may Allah have mercy on him) narrates from his father, who said: A woman from Banu Layth bought me in the market of Dhu al-Majaz for 700 dirhams. Then I came to Madinah, and she made a contract of manumission (mukatabah) with me for 40,000 dirhams. I paid her most of that amount, then I carried what remained to her and said: Take possession of your money. She said: By Allah, (no,) I will take it month by month and year by year. I went and mentioned this to Sayyiduna Umar bin al-Khattab (may Allah be pleased with him), and he said: Deposit the money in the public treasury (Bayt al-Mal). And he sent word to her: Your money is in the public treasury, and Abu Sa'id is free; if you wish, you may keep taking it month by month and year by year. He said: Then she took the money.
Abu Bakr al-Naysaburi said: This hadith is hasan (good).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21708