If the bleeding ceases after 40 days following childbirth, but then returns intermittently during two days of fasting, what is the ruling?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Whenever the post-natal bleeding (Nifas) ceases and the woman is certain it will not return, she has become pure; therefore, she must perform the ritual bath (Ghusl) and resume praying and fasting. However, if the blood returns within fifteen days of its cessation and before sixty days have passed since the delivery, the ruling of Nifas applies once again. Consequently, any fasting or prayer performed during that interval of purity is rendered invalid; she must make up for the missed fasts of those days, but she is not required to make up for the prayers. And Allah the Exalted knows best.
Can someone who begins a voluntary fast break it?
It is preferable for someone who begins an act of worship not to break it.
Allah the Exalted has said {what means}: "and let not your [good] deeds come to nought!" [Muhammad/33].
However, if a person starts a voluntary fast (nafl) and needs to break it, they are going against what is preferable, but there is no sin upon them.
If a person enters a mosque and finds the congregation in the final tashahhud, which is more virtuous — joining them or waiting for a second congregation to catch the opening takbīr (takbīrat al-iḥrām)?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
If a worshipper finds a congregation that is about to finish its prayer, and he hopes to catch the entire prayer from the beginning with another congregation, it is more virtuous for him to pray with this first congregation and then repeat the prayer with the second one — provided he does not intend to confine himself to a single prayer. If, however, he intends to perform only one prayer, then it is more virtuous for him to wait for the second congregation rather than joining the first, so that he may attain the reward of congregational prayer for every single rakʿah.
Al-Khaṭīb al-Sharbīnī, may Allah have mercy upon him, states: "If members of a congregation enter the mosque while the imam is in the final tashahhud, al-Qāḍī Ḥusayn held that it is recommended for them to join him in prayer, and that they should not delay in order to form a second congregation. Al-Mutawallī, however, affirmed the opposite view, and al-Qāḍī's own statement elsewhere supports this latter position, which is the relied-upon view. In fact, it is more virtuous for a person who has missed part of the prayer with one congregation, and who hopes to catch another congregation with whom he can attain the entire prayer within its proper time, to delay so that he may catch it in full with them. This applies when he intends to confine himself to a single prayer; otherwise, it is more virtuous for him to pray with the first group and then repeat the prayer with the others." [Mughnī al-Muḥtāj,Vol. 3/P.186] And Allah the Almighty knows best.
What is the ruling on the ablution of one who cuts his nails, and is it permissible to cut them before the ritual bath for major impurity (janabah)?
Cutting nails does not invalidate ablution, and it is permissible to cut them before the ritual bath for major impurity. And Allah the Almighty knows best.