Abu Bakr says that a man made a contract of manumission with his slave, fixing it in set installments. The slave brought his entire contract payment, but he refused to take it except in installments. He came to Sayyiduna Umar (may Allah be pleased with him), and Sayyiduna Umar (may Allah be pleased with him) summoned his master and offered him the payment, but he refused to take it. Sayyiduna Umar (may Allah be pleased with him) said: I will deposit it in the public treasury. And he said to the master: Take your fixed installments, and he said to the mukatab: Go wherever you wish.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21709