Minimum number of slaves to be purchased when funds are sufficient for three
General Chapter
Al-Mughni
Book of Bequests
Primary text
If the allocated third of the estate is sufficient for purchasing three slaves, it is not permissible to purchase fewer than three. This is because three constitutes the minimum number for a collective group. If the full third can purchase more than three slaves by choosing cheaper individuals, that is preferable and superior. This preference is supported by the Prophet's statement regarding the reward for manumitting a Muslim woman: 'Allah will free a limb for every limb of his from the Fire.' Furthermore, freeing an additional soul is better than the absence of that.
Supporting text
If the choice is between purchasing three expensive slaves or purchasing three cheap slaves plus a share of a fourth using the price of the expensive three, the three slaves are prioritized. This is based on the Prophet's response when asked about the best slaves to free: 'The most valuable among them in price and the most cherished by their owners.'