What is the ruling on performing istinja' before every ablution?
Istinja' is not from the conditions for the validity of ablution. It is only obligatory for prayer when there is impurity from urine or stool on the private part, or if there is fear of the impurity spreading to the body or clothing. And Allah the Almighty knows best.
Is it permissible for a wife to give her money to her family as a charity, or a gift without asking her husband, or seeking his consent?
The wife has the right to give her money as a charity, or a gift to her family, or to other people after consulting her husband out of respect, and this is the meaning of treating on footing of kindness and equity. Therefore, if he wanted to stop her from helping her family, then there is no harm in not telling him.
Should the Zakah (obligatory charity) giver tell the poor recipient that this is the Zakah of his money?
No, he shouldn`t. But, the Zakah giver should make an intention in his heart that it is the Zakah of his money when paying it to the poor. And Allah Knows Best.
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]