What is the wisdom behind the legislation of fasting?
Fasting is a divine school from which the believer learns much and trains in virtues that may be needed in life. Among these virtues is patience, as it is the month of patience. Fasting also teaches honesty and consciousness of Allah in both private and public, for there is no observer over the fasting person in abstaining from lawful pleasures except Allah alone.
Fasting strengthens willpower, sharpens determination, and nurtures mercy and compassion among the servants of Allah. It is a struggle against the self, a restraint of desires, a purification of the soul, and a cultivation of goodness.
The Prophetﷺ said: "Allah, the Almighty, said: ‘Every deed of the son of Adam is for him, except for fasting; it is for Me, and I shall reward for it. Fasting is a shield. So when one of you is fasting on a day, let him not engage in obscene speech or raise his voice in anger. If someone insults him or fights him, let him say: I am a fasting person. By Him in whose hand is the soul of Muhammad, the breath of the fasting person is more pleasant to Allah than the fragrance of musk.’" [Bukhari and Muslim]
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.
What is the Du`a (supplication) of Istikhara (guidance prayer)?
O Allah, I consult You as You are All-Knowing and I appeal to You to give me power as You are Omnipotent, I ask You for Your great favor, for You have power and I do not, and You know all of the hidden matters. O Allah! If you know that this matter (then he should mention it) is good for me in my religion, my livelihood, and for my life in the Hereafter, or he said: "for my present and future life" then make it (easy) for me. And if you know that this matter is not good for me in my religion, my livelihood and my life in the Hereafter, or he said: "for my present and future life" then keep it away from me and take me away from it and choose what is good for me wherever it is and please me with it."
What is the ruling of Islamic Law on someone who wakes up in a state of janābah (major ritual impurity) near the very end of the prayer's designated time, during cold weather — should he heat water in order to perform ghusl, even though the prayer's time will expire as a result, or should he perform tayammum instead?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
If the water is cold, and cannot be used due to fear of harm that is not ordinarily tolerable, or that would result in illness, then in this case it becomes obligatory to heat the water — even if heating it causes the time for Fajr to expire — and no sin is incurred in doing so, due to his valid excuse. He may not resort to tayammum (dry ablution) instead, since water remains available [and merely needs to be heated].
Imam Shihāb ad-Dīn Aḥmad ar-Ramlī (raḥimahullāh) said: "He was asked regarding a person who, if he were to use cold water, would experience harm that permits tayammum, and who has access to something with which he could heat the water — but if he heats it, the prayer's time will expire. Is it obligatory for him to heat it even if the time expires, or should he pray with tayammum within the prescribed time? He answered that it is obligatory for him to heat the water, even if the time for that particular obligatory prayer expires." [Fatāwā ar-Ramlī, Vol.1/P.98]
Imam al-Bājūrī (raḥimahullāh) said in his Ḥāshiyah on Sharḥ Ibn Qāsim (Vol.1/P.173): "And if he fears [harm] from using cold water, and is currently unable to heat it, but knows of a place where firewood is available, such that if he were to go there he would not return until after the prescribed time has expired — what appears [to be the correct position] is that it is obligatory for him to go and seek the firewood, even if the time expires as a result, as this is the position ultimately settled upon by ar-Ramlī, and as related from him by Ibn Qāsim." And Allah, the Exalted, knows best.