Upon exercising the option to revoke (Khiyar) in a sale involving the manumission (Ataq) of a slave, whose manumission is effective?

Primary text

If one party manumits the slave, the manumission of the one whose ownership we rule valid takes effect. The apparent ruling of the school (Dhahir al-Madhab) is that ownership resides with the buyer, thus the buyer's manumission takes effect, whether the option belongs to both parties or only one. This is because it is the manumission by an owner legally capable of disposing of property, thus it is effective, similar to the period after the option has expired. The statement of the Prophet, peace be upon him, 'There is no manumission concerning that which Adam's son does not own' implies by its negative implication that it takes effect regarding owned property. The seller's right to annul the sale does not prevent the manumission from taking effect, similar to when a seller sells a male slave for a specific female slave; the buyer of the male slave's manumission is effective even though the seller has the right to annul the sale. Likewise, if a man grants his son a slave, and the son manumits the slave, the son's manumission is effective despite the father's right to reclaim it.