What is the distribution of maintenance liability when a slave is married to a woman who spends time in both his and his master's dwelling?

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Maintenance is distributed such that the husband owes maintenance for the time she spent with him at night, as this fulfills the requisite permission for cohabitation. The remaining maintenance for the time she spends with the master is due from the master, by virtue of her being his property, for whom no one else owes maintenance during that time. Thus, each owes half the maintenance. This is one opinion of Al-Shafi'i.