Do the husband's sister and paternal aunt remain in the category of guests after the first three days of their forty-day stay, and must the wife serve them, and is the husband entitled to punish her if she falls short in that?

It is the guest's right to be honored for three days, and anything beyond that is charity. Regarding a wife serving her husband's guests, there is a difference of opinion among jurists. According to the view that it is obligatory, the husband should not burden his wife with what she cannot bear, and the husband's family should not overburden the household. A husband may discipline his wife when she is disobedient (nashūz), and according to the view that service is obligatory, discipline is permissible within the bounds of Islamic law. There should be understanding between the spouses, and if the husband is able, he can bring a servant, especially if the wife is someone who does not serve herself, as it is her right for her husband to provide a servant.