It is narrated from Hasan (may Allah have mercy on him): A man bought a slave for seven hundred dirhams, then set him free, but did not pay the price of the slave, nor did he leave any other wealth. Sayyiduna Ali (may Allah be pleased with him) said regarding this: The slave will work and labor according to his price. (That is, he will become free after paying that amount.)
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3304
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده صحيح إلى علي، [مكتبه الشامله نمبر: 3315]
Hadith Takhrijاس اثر کی سند صحیح ہے، اور ابوالولید کا نام ہشام بن عبدالملک الطیالسی ہے۔ دیکھئے: [عبدالرزاق 16766] ، [ابن منصور 415]