What are the conditions for repentance for a person who has engaged in usury, and how should they act if they cannot accurately determine the usurious amount, or if the money they possess is less than the usurious amount they previously acquired? And must they donate everything that exceeds their basic needs before performing Hajj?

Allah the Almighty says in the verse about usury: "So whoever receives an admonition from his Lord and stops, له ما سلف (then what has passed is his), and his affair is to Allah." This means that whoever is informed of Allah's prohibition of usury and stops, then what has passed from his dealings before the prohibition is his, and he is not required to return what he took as usury before he knew of the prohibition. As for what he took as usury after he knew of the prohibition, he must return it. If it has mingled with his wealth and he does not know how much it is, then he should estimate it and give it out.