Rabi'ah bin Abi Abd al-Rahman (may Allah have mercy on him) says that in the time of Aban bin Uthman (may Allah have mercy on him) a man freed all of his slaves. Aban bin Uthman (may Allah have mercy on him) gave orders concerning all the slaves; they were divided into three groups, and then lots were drawn between them. Whoever's lot came out was to be freed; the lot came out for one of the groups, and they were freed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21401