What is the ruling when a testator wills for a slave to be purchased with a specific sum (e.g., 1000) for emancipation, but this sum exceeds the one-third disposable portion?

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If the specified amount for purchasing the slave exceeds the one-third disposable portion (Thuluth), the purchase is executed using only the amount covered by the one-third. This is the position held by Imam Al-Shafi'i. The reasoning is that this bequest is obligatory to execute to the extent that the one-third allows, analogous to a bequest to free a slave where only the portion covered by the one-third is freed. This differs from agency (Wikalat), as an agent authorized to free a slave cannot free only a part of him, whereas a testator's bequest allows for partial execution against the estate.