Is a mortgaged slave permitted to have sexual relations with a concubine without the master's permission?

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A slave with a partial ownership status (mukātab, or slave progressing towards manumission) is prohibited from taking a concubine without the explicit permission of his master because his ownership is incomplete. The reasoning provided is that his ownership is deficient, and permitting this act harms the master, similar to how marriage is restricted under these circumstances. The harm arises because the concubine might become pregnant, and this pregnancy creates complications; she might die, or she might give birth, becoming an Umm Walad (mother of his child), which prevents her sale to cover the cost of the slave's manumission contract. If the contract fails, the ownership returns to the master in a diminished capacity. If the master grants permission, the act becomes permissible.