What is the legal basis for treating the freeing of slaves upon condition as an immediate manumission rather than a conditional oath?

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The manumission of slaves contingent upon a condition is legally effective when the condition is met because the subject (manumission) is capable of being suspended, similar to divorce, and the general Quranic verse concerning expiation is specific to divorce. Furthermore, manumission is not inherently an oath; it is a suspension based on a condition, thus resembling divorce. Regarding the narration of Abu Rafi', Ahmad stated that the command was to offer the expiation of the oath and to free the female slave, indicating that the command to free the slave must be accepted, or it may be that she owned no other slave besides the one mentioned.