Is a woman obliged to seek her husband’s permission to do supererogatory prayers and tahajjud?
Question

I have read voluntary hajj,fast needs permission from husband since those are not fard, but what about tahajjud and sunnah prayers in obligatory five prayers as well.if yes,do we have to ask permission every time we want to pray the voluntary prayers or once he has mentioned no to it ,is sufficient. if husband puts such condition in marriage contract ,is it to be obliged forever by wife . What if he permits by himself even after writing in marriage contract? Does that affect the contract or makes him sinful?
Praise be to Allah.Firstly:
Ruling on a woman seeking her husband’s permission to do supererogatory prayers and tahajjud
A woman is not obliged to seek her husband’s permission to do supererogatory prayers and tahajjud, because they only take a short time, in contrast to fasting and Hajj, which take a long time and may be detrimental to the husband.
Al-Khateeb ash-Sharbeeni (may Allah have mercy on him) said:
It is haraam for a woman to observe a voluntary fast when her husband is present (not travelling), except with his permission, because of the report in as-Saheehayn which says: “It is not permissible for a woman to fast when her husband is present, except with his permission.”
That is because fulfilling the husband’s right is obligatory, so it is not permissible to refrain from doing that in order to do a supererogatory act of worship.
If she fasts without his permission, the fast is valid, even if it is haraam, which is similar to the case of prayer offered in a house that was seized by force.
Knowing that the husband approves of that is the same as his giving permission.
We will see below that it is not haraam for her to fast the day of ‘Arafah and ‘Aashooraa’.
As for her fasting when her husband is absent from her city, that is permissible, and there is no difference of scholarly opinion concerning that.
If it is said: Why is it not permissible for her to fast when he is present, and if he wants to be intimate with her he may do so, and her fast will be invalidated?
The answer is that her fasting usually prevents him from being intimate with her, because he is afraid to violate the sanctity of the fast.
Supererogatory prayers cannot be compared to fasting, because they take a short time." (Mughni al-Muhtaaj  2/187).
Secondly:
The husband does not have the right to stipulate that his wife should ask him for permission to do supererogatory prayers
The husband does not have the right to stipulate that his wife should not do any supererogatory prayers except with his permission. This is an invalid stipulation that serves no interest for the husband, because the prayers only take a short time, as noted above, and because if he wants to be intimate with her and calls her whilst she is offering a supererogatory prayer, she may exit her prayer for that purpose, according to a number of fuqaha’.
According to those scholars who do not allow her to exit her prayer, the matter is easy, because he can wait until she ends her prayer, and she can make her prayer shorter in that case.
It says in Kashshaaf al-Qinaa‘ (1/379): It is permissible for the wife to exit a supererogatory prayer to fulfil the husband’s right, because that is obligatory, so it takes precedence over the supererogatory prayer, in contrast to the obligatory prayer. End quote.
And Allah knows best.