Is it permissible for someone to make a supplication to Allah to marry an already married, or an engaged woman?
No, it isn`t, and the person who does so is sinful before Allah, The Almighty.
If a woman makes a vow to slaughter a sheep, and her husband is the one who buys it for her from his own money, and he says: "It is for you until you fulfill your vow with it," Is this permissible, or must she buy it herself from her own money?
If her husband gave her the sheep as a donation for the puprose of fulfilling the oath she made and was slaughtered by the wife or the husband on her behalf then the vow she made is fulfilled. And Allah Knows Best.
What is the ruling on reciting verses of the Holy Quran on water, then drinking it?
It is permissible to recite Quran on water, then drink it as a kind of treatment since the Quran heals. Allah, The Almighty, Says (What means): "We send down (stage by stage) in the Qur’an that which is a healing and a mercy to those who believe: to the unjust it causes nothing but loss after loss." [Al-Isra`/82].
My mother inherited a share from my late father`s and brother`s property; however, the inheritance, a piece of land, wasn`t divided amongst the eligible heirs because it was hard to sell. While alive, she used say that she wanted these shares to be distributed amongst the poor and needy. What is the ruling of Sharia on this?
All perfect praise be to Allah, the Lord of the worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
This is a will, so we have to consider the estate she had left behind. If the piece of land, which she had willed, equals one third and less of her estate, then the will must be executed. But, if it is more than one third, then one third must be executed and the rest of the estate, if the heirs agreed, is to be executed as part of her will as well. However, if the heirs haven`t approved of that, then what remains, excluding that one third, must be divided amongst them according to the Islamic rules of inheritance. Moreover, we recommend that you pay a visit to the Iftaa` Department to make things clearer for you. And Allah The Almighty Knows Best.