it is permissible, because he has already made up the amount of what he missed from the night. The other [viewpoint] is that it is not permissible, due to the lack of equivalence. Once this is established, it is impossible for him to make up all of it from the other wife's night, lest the right of the other wife be missed, which would then require making it up. Instead, he must either isolate himself for a night and make it up from it, or divide a night between them, favoring this one by the amount of what she missed of her right, or leave from the night of each of them an amount equal to what was missed from the night of this one, or divide the portion left out between them, such as if he leaves two hours from the night of one of them and makes it up for her from the night of the other by one hour, so that what is missed by each of them becomes one hour.

Section: As for entering upon her co-wife during her time, if it is at night, it is not permissible except out of necessity, such as if she is afflicted with something and he wishes to attend to her, or she leaves him a bequest, or something that is unavoidable. If he does that and does not linger, he does not have to make it up. If he stays and the sick woman recovers, he makes it up to the other from her night by the amount he spent with her. If he goes out for a non-essential need, he completes it. The ruling regarding making it up is the same as if he entered out of necessity, [if he did not linger, he does not make it up] (8), because there is no benefit in making up a small amount. If he enters upon her and has intercourse with her in a short time, there are two viewpoints regarding this; one is that he is not obligated to make it up, because intercourse is not a right in the division, and a short time is not made up. The second is that he is obligated to make it up, which is to enter upon the aggrieved wife during the night of intercourse and have intercourse with her, so as to be equitable between them, and because a short time combined with intercourse results in intimacy (sakan), so it resembles a long time. As for entering during the day upon a wife during someone else's day, it is permissible for a need, such as delivering maintenance, or visiting the sick, or asking about a matter he needs to know, or visiting her due to a long absence, and the like; based on what Aisha narrated, who said: The Messenger of Allah (peace and blessings of Allah be upon him) used to enter upon me during a day that was not mine, and he would enjoy everything from me except intercourse (9). When he entered upon her, he did