My father placed shares worth twenty dinars in one of the banks, and their value doubled to become five thousand dinars. When my father passed away, one of the scholars told us that it is permissible for us to take the money. What is the ruling on this money, considering that it comes from a bank and involves interest (Riba)?
Allah The Almighty Said (What means): "And if you repent, then for you is the principal of your wealth. You do not wrong, nor are you wronged." [Al-Baqarah/279]. This is the precautionary ruling regarding what you are asking about. You are entitled to the principal amount, and you should give the excess as charity to the poor and needy. If you are poor, you may take from it. And Allah The Almighty Knows Best.
Is it permissible to swear by (Allah "The Living")?
Yes, it is permissible because "The Living" is one of Allah`s Attributes.
Someone asked me to pay off his debt on his behalf as a loan, without any compensation. When I went to the creditor, he told me that if I paid the full amount at once, rather than in installments, he would give me a certain discount. Is this permissible? And if he applies the discount, to whom does the deducted amount belong?
If part of the debt is paid and the creditor forgives the remaining amount, the waiver is valid, and the remaining debt is no longer the responsibility of the original debtor. The person who paid the debt on behalf of another has no right to claim any portion of the original debt. And Allah Knows Best.
What is the ruling on a Muslim who slaughters an animal while being in a state of Janabah (ritual impurity)?
All Perfect Praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upo all of his family and companions.
Slaughtering is permissible for the ritually impure man and the menstruating woman because ritual purity isn`t a condition for the validity of the slaughtering. Moreover, it is permissible for the uncircumcised person to do the slaughtering as well. And Allah The Almighy Knows Best.