Interest acquired before it was known to be forbidden
11-5-2015 | IslamWeb
Question:
Assalamoalaikum,Answer needed immediately,My maternal grandmother gave me 50000 rs for educational purpose from her pension,I consumed some 30000 rs, and 20000 rs is left with me,My queston is ,that What will I have to do now with the remaining money as She never had paid interest which she got from the bank account from last 20 years(she is gettting the pension from last 20 years),Till now I and She was unknown of the fact that it is Illegal to consume interest money.I will have to return whole or remaining money to her?What my Grandmother should do with that money?Also when I go to her house in vacation,Is it permissible for me & my family to eat from her money as She and Her Son(my uncle) take care of the food and daily needs of the house and my uncle too didnt gave interest money to the poor from his bank account?Main verdict is that My grandmother should give interest money from last 20 years or now onwards?Is there any way to know how much interest we have got till now from our bank, as it is impossible to find old passbooks?Please answer directly donot refer to any other fatwas.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
There is no blame on you for using what your grandmother has given you, be it what you have already consumed or what remains in your possession. There is no blame on you for eating her food or her son's food because it is permissible to interact financially with someone whose wealth is mixed from lawful and unlawful earnings, especially if the unlawful earnings are less than the lawful earnings. Please, refer to Fatwa 84481.
As for the ruling on using the interest money she had acquired before knowing the prohibition and whether she is obligated to dispose of it or not, some scholars held that one is not obligated to dispose of the interest money obtained before knowing about the prohibition, be it what he has already consumed or what remains in his possession. Allaah The Exalted says (what means): {So whoever has received an admonition from his Lord and desists may have what is past, and his affair rests with Allaah.} [Quran 2:275]
Although this verse was revealed in relation to the ruling on the usury received by disbelievers before embracing Islam, it also applies to the Muslim who is excused because of his ignorance if he repents of his sin (of dealing in usury). In fact, it applies to him with even more reason.
The following appears in the Al-Fataawa Al-Kubra of Ibn Taymiyyah 
: “If one earns unlawful money with the consent of the giver then he passes away, such as the price of alcohol or a dog or fees paid to a prostitute or a magician, it can be summarized from the pronouncements of Abul-‘Abbaas that if the earner is not aware of the prohibition and knew of it after earning this unlawful money, it is permissible for him to use it. However, if he knew the relevant prohibition while obtaining these unlawful earnings and then repented of his sin, he should offer this unlawful money in charity as Imaam Ahmad stated regarding the bearer of alcohol.” [End quote]
For more benefit, please refer to Fatwa 85917.
As for the interest money she earned after knowing the prohibition of such an act, it is incumbent on her to dispose of it by donating it to the poor and needy. Also, she should not keep her money in that usurious bank any longer. She is obligated to withdraw her money from that bank.
Based on that, there is no harm in using the interest money earned in the past before the prohibition was known and it is not necessary to know the amount. However, the earner is obligated to dispose of the interest money which was obtained after knowing the ruling. If this unlawful money is easily identified and the earner knows its exact amount, this is great. If not, he should use his best judgment to estimate its amount.
Allaah Knows best.