What should a person who borrowed with interest(Ribba) do?
Question

                Salam Brother, 
My question is; how does one purify himself or his place of business from things 
that may have occurred prior to knowledge that it was haram? For example, I own 
clothing stores, but have financed this business via moneys borrowed and paid 
interest upon. To this day I am using a bank where I have a loan and pay interest 
on it. 
Also in the past I had a business that did not succeed, and was forced into 
bankruptcy, which meant that there were many people and businesses that were 
left unpaid, what is my Islamic duty in that case? I did make a sincere effort to pay 
all that I could but after the business went bad was not able to repay them.
Praise be to Allah.It is wajib that you repent for each loan involving interest you took. The Prophet (peace and 
blessings of Allah be upon him) cursed all involved in the interest, the recipient, the sponsor, 
and the one eating and the feeding it, as stated in the authentic hadith. The Prophet (peace 
and blessings of Allah be upon him) said, "The gold for the gold, the silver for the silver, 
wheat for wheat, barley for barley, date for date, salt for salt, similar for the like, and hand 
in hand. So whoever adds or seeks to add, then he has used riba. The recipient and the giver 
of the transaction are the same". (Reported by Muslim, #1584.)
On the authority of Jabir (may Allah be pleased with him) who said that the Messenger of Allah 
(peace and blessings of Allah be upon him) "cursed the one who consumes interest, the one 
giving it, the one bearing scroll, and the two witnesses to it". He said (peace and blessings 
of Allah be upon him), "they are all equal." (Muslim narrated it.) 
If a Muslim wants to partake in a specific affair and he doesn't know it's ruling, then it is upon 
him to ask before he gets involved in it. Ignorance isn't an excuse for each and every situation. 
As far as the loans you borrowed, you are obligated to return the initial money borrowed only. 
If you are forced to pay riba, and that is the added amount with no way out, then we hope that 
you do your best in repenting to Allah to pardon you. We also hope that you remain consistent 
in your business and give sadaqa with what you are able to, in order to purify yourself and your 
wealth. 
We ask Allah to enrich us with His halal and to avoid His haram.