The ruling on whoever takes this Interest ignorantly
Question :
If I had a sum of money, and I put it into a bank, and a period of time passes on that money - let's say a year or more. Then, I received the money with an increase of 10%, and I did not know that this was a type of Riba or dealing that is not legislated. I spent the entire amount, meaning the increase that I gained, and the rest remained in the bank. Can I give this same amount (in charity) from any amount that I own from my lawful earnings, and is it permissible for me to travel to give it to my female cousins who are married and in need? This is while knowing that they live in an area that is far away from us.
You must repent from what you devoured (i.e., used) of that Riba that the bank gave to you in the name of "interest". You do not have to pay any fine or charity. Rather, this is from that which Allâh pardons due to His Statement:
"So, to whomever an admonition comes from his Lord and he desists (from Riba dealings), then for him is whatever passed (that he took of Riba before) and his matter is left to Allah."
So, if you took this Riba after that (i.e., knowing it was Riba), then you should spend it in charity on whoever deserves charity among your relatives or non-relatives. This is so that you can clear yourself of the sin of devouring Riba.
Source:
Ash-Shaykh Ibn Jibreen
Fatawa Islamiyah, Vol. 3 Pages 402-403