It tells that it is forbidden to divorce a woman while she is having her menses, and whoever does so by mistake should receive back his wife after the divorce. In case the husband remained of the same mind, the divorce ought to be given at the time of purification after menstruation provided that he had not made love to her during it.
The idea behind the arrangement is that during menstruation, a woman is not fit for sexual intercourse while, in the state of purification, it is quite possible that the husband felt inclined towards her and the intention to divorce disappeared from his heart which, in any case, is more pleasing to the Lord and the Apostle.
In the incident related above, Abdullah bin Omar was told by the holy Prophet (saws) to take back the divorce he had given and allow a period of purification to pass, and if, even then, he was adamant, he could divorce his wife during the second period of purification, the idea being that when the two would live together during the whole of the intervening period of purification, the relations might improve and the divorce avoided. But if it did not turn out that way and the divorce was inevitable, the Prophet advised Abdullah bin Omar to do so during the second period of purification, before cohabitation. This last condition, too, was based on the logic that the sexual urge was stronger at the close of the menses, and it might, also, offer a hindrance to divorce.
It, further, shows that though divorce is forbidden during menses and is a grave sin, it does take place if given. Were it otherwise, there would have been no need for restitution, and instead of telling Hazrat Abdullah bin Omar to receive back his wife, the holy Prophet would have said that the divorce was void.