And because having intercourse with his female slave is a meaning that prohibits her sister due to the cause of combining [two sisters], it prevents the validity of marrying her, just as in the case of marriage to a free woman. It differs from purchase, as purchase is not intended for intercourse; for this reason, the purchase of two sisters—or those who are not lawful for him—is valid. Their claim that "marriage is stronger than intercourse by ownership of the right hand" is contested. Even if it were granted, the intercourse is earlier in time, so it is given precedence and prevents the validity of what subsequently occurs that would contradict it, just as the waiting period ('iddah) prevents the initiation of the marriage of a sister. Likewise, intercourse with a female slave prohibits marriage to her daughter or her mother. This is because this act is equivalent to marrying a sister during the waiting period of her sister, due to his failure to observe the period of innocence (istibra') for the woman with whom he had intercourse.

Section: If he marries off the female slave with whom he had intercourse, or removes her from his ownership, he may then marry her sister. If the female slave returns to his ownership, the marital relationship remains as it is, and her lawfulness continues, because the marriage is valid and is stronger, and the female slave is not lawful for him. Another narration states that one of them must be prohibited, because his female slave, who was a bed, has returned to him, and the one married is used as a bed, so it resembles his two female slaves, one of whom he had intercourse with after marrying the other, then the husband divorced her sister. If he marries a woman, then buys her sister, the purchase is valid, but she does not become lawful for him, because marriage is like intercourse, so it resembles the case where he had intercourse with his female slave then bought her sister. If he had intercourse with his female slave, both become prohibited to him until he observes the period of innocence (istibra') for the female slave; then his wife becomes lawful for him, but not his female slave, because marriage is stronger and earlier in time. The period of innocence was only required so that he would not be gathering his semen in the womb of two sisters. It is also possible that both are prohibited to him until one of them is prohibited, as in the case of two female slaves.

1154 - Issue: He said: "The paternal aunt of a female slave and her maternal aunt are in that regard like her sister."

He means in the prohibition of combining them in intercourse, and the detailed discussion regarding them is the same as the detailed discussion regarding two sisters, according to what we have mentioned.