Is it permissible for a woman to lead other women in prayer?
Yes, it is permissible for a woman to lead other women in prayer. The most knowledgeable among them in the rulings of prayer should act as the imam. She should stand in the middle of the row, slightly ahead of the others.
Is the niṣāb calculated based on the price of 21-karat gold, or 24-karat gold?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Zakāh is obligatory on cash and on gold designated for saving or for trade, provided the total reaches the niṣāb (minimum threshold liable for zakah), and a full ḥawl (lunar year) has elapsed over it. The niṣāb is (85) grams of 24-karat gold; for 21-karat gold, the niṣāb equals (97) grams; and for 18-karat gold, it equals (113) grams.
The relied-upon position is to calculate the zakāh based on the buying price [i.e., the price the gold merchant would pay the owner to purchase the gold from him] on the day the zakāh obligation is due.
The one paying zakāh may assess/calculate the niṣāb using any of the aforementioned gold karats [i.e., he may choose whichever karat standard he wishes for the purpose of the calculation]. And Allah, the Exalted, knows best.
Is it permissible for someone with a physically demanding job, such as a baker or construction worker, to break their fast?
It is not permissible for someone with a physically demanding job to start the day intending to break their fast. They must make the intention to fast at night and begin fasting. However, if they reach a point where fasting becomes unbearably difficult, they may break their fast and make up for it later.
What is the ruling on the follower`s prayer if the Imam stands for a fifth rak`ah?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
If the Imam stands up for an extra unit (rak‘ah) of prayer out of forgetfulness, he must return to the sitting position as soon as he remembers, and he should perform the prostration of forgetfulness (Sujud al-Sahw). It is the duty of the congregants (Ma’mumin) behind him to remind him. However, if the Imam is in a state of doubt regarding the extra unit (and not certainty), it is not permissible for him to return.
As for the congregants: anyone who is certain that the Imam has stood for an extra unit is forbidden from following him. In this case, the follower has two choices: either intend to separate from the Imam (Mufaraqah) and finish the prayer alone, or wait for the Imam in the sitting position and perform the final salams with him—the latter being the preferred option. If a follower knowingly follows the Imam into an extra unit, their prayer becomes invalid. However, if a follower is in doubt and not certain of the mistake, they must continue following the Imam, as the Imam was appointed to be followed.
It is stated in Al-Majmu’ (Vol.4/P.145): 'If [the Imam] stands for a fifth rak‘ah, the follower should not follow him, even if it is assumed that the Imam might have omitted a pillar from a previous unit; because if the reality is known, following him is impermissible since the follower has certainly completed their own prayer. Even if the follower had missed a previous unit (Masbuq) or was in doubt about performing a pillar like the Fatihah, and the Imam stood for the fifth, it is not permissible for the latecomer to follow him in it. This is because we know that this unit is not counted for the Imam and that he is mistaken in performing it.' And Allah the Exalted knows best.