Is the sale valid if a master sells a sexually possessed female slave without performing *Istibra'*?

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The prevailing view is that if the master sells her without *Istibra'*, the sale is outwardly valid because the presumption is the absence of pregnancy. This is supported by the report that when Umar judged the dispute between Abdur-Rahman ibn Awf and the buyer of the pregnant slave, Umar and Abdur-Rahman only addressed invalidity or consequences upon the confirmed arrival of the child, implying the sale was not void beforehand. The obligation of *Istibra'* falls upon the buyer to preserve his semen, thus it is not necessitated upon the seller. Conversely, some scholars argue that *Istibra'* is required of the seller because it is necessary for the buyer to preserve his semen, and until *Istibra'* is done, the validity of the sale is questionable due to the possibility that she might be an *Umm Walad* (mother of the master's child). Umar reportedly criticized Abdur-Rahman ibn Awf for selling the slave woman before seeking purification, and when pregnancy was confirmed, the child was attributed to Abdur-Rahman.