What is the ruling regarding a husband divorcing his wife in the last days of her menstruation, after she had performed ghusl and prayed Dhuhr, and then a few drops of blood appeared on her after Dhuhr, causing her to stop praying?

Divorce becomes effective upon a woman in all circumstances, whether during her menstrual period or post-natal bleeding (istihadah (definition)). The divorce of a menstruating woman is effective according to the four imams and the majority of scholars, even if the one divorcing is sinful. As for bleeding after purity, if it is istihadah, the divorce is effective and there is no sin in it, because a woman experiencing istihadah has the rulings of pure women. If it is menstruation, then a divorce that occurs during an intervening period of purity is considered a Bidah divorce (innovative divorce) by some scholars, and the husband may be compelled to take her back if the bleeding resumes before the completion of purity. As for abandoning prayer, if it was during menstruation, there is no need to make up the prayers. If it was during istihadah, then it is obligatory to make up all missed prayers.