Exchanging currency and adding what one spends in this regard

Q: I live off of my mother's pension which she receives from France (Part No. 11; Page No. 94) where my father used to work. We exchange the currency as follows: We commission a person who gives us the money in Algeria in Dinars and then goes to a bank in France where he gets francs and vice versa in France where he takes francs from the bank also as our agent and when he returns to Algeria, he gives us dinars. The exchange rate is one franc to fourteen Algerian dinars. I asked some brothers here who said that this is Riba Al-Nasi'ah (usury of delay, conditional excess for delay of payment). Our house was built from this money and we spend from it on our food and drink and everything else. My tuition fees, books and clothes are likewise from it. I also used to give Sadaqah (voluntary charity) and observe voluntary Sawm (Fast), but when I learnt that this money is Riba, I stopped because Allah does not accept any act except that which is good. I have lost hope because whenever I think about this, I find that everything in my life is from a Haram (prohibited) source and think that how can Allah (Glorified and Exalted be He) accept acts of worship from me when my food is Haram, my drink is Haram and my home is Haram. My enthusiasm for my studies has waned and I maintain that the certificate I will receive is from Haram sources. What should I do?

A: If your agent gives you Algerian dinars before he travels to France by way of a loan and then after he takes your father's pension from the bank in French francs, and gives you the money according to the exchange rate of dinars and francs in Algeria and does not stipulate an increase in price, then there is no sin in this. This is because of the narration of Ibn ‘Umar (may Allah be pleased with him and his father) who said: O Messenger of Allah! I (Part No. 11; Page No. 95) sell for Dinars (old Arab coin that equals 2.975 grams of gold) but receive the price in Dirhams (a dirham of silver equals 2.975 grams of silver) and I sell for Dirhams but receive the price in Dinars. The Prophet (peace be upon him) said: There is no sin provided that when you take the price, it corresponds to the current market price and there are no outstanding accounts between the both of you. However, if this man gives you the Dinars before he travels by way of exchanging French currency which he will receive after he travels, this is impermissible because he will not be paid in the same sitting as the contract. What you have previously done with regard to contravening the Shari`ah (Islamic law), you are not blameworthy for it and it does not factor into the validity of your Salahs or any other act of worship due to the words of Allah (Glorified and Exalted be He): So whosoever receives an admonition from his Lord and stops eating Ribâ (usury) shall not be punished for the past; his case is for Allâh (to judge) It is a duty upon a Muslim to offer Tawbah (repentance to Allah) to Allah for being negligent and to think well of Allah since sincere Tawbah is sufficient to wipe away the sins of those who sincerely direct their acts of worship to Allah Alone.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.