How can a mother rid herself of the sin of usury that she unknowingly committed by using usurious interest to buy furniture for the house, and is it obligatory to give money in charity in exchange for this interest after withdrawing all the money from the bank?

The one who repents from usury must give the usurious money in charity to the poor or for the benefit of Muslims, according to most scholars. However, if he is poor, he may spend from it according to his need. But if he is wealthy or spends the money on something other than his need, he must dispose of the usurious money. Sheikh al-Islam Ibn Taymiyyah held the view that the one who repents from usury is not obligated to dispose of the illicit money, and "what has passed is his"; because of Allah’s saying: "So whoever receives an admonition from his Lord and desists, he may have what has passed, and his affair rests with Allah."