What should I do to atone for my sin after I found a large sum of money in a clothing store and spent it, knowing that I was in financial and psychological distress and thought that God had provided it for me, but now I feel remorse and fear of God?

If someone finds a valuable lost item (luqata), they must announce it for a period of one year in public gatherings two or three times each month. If its owner is identified, it should be handed over to them. Otherwise, it becomes their property after the year. However, if the owner appears at any time, it is obligatory to return it to them. As for an insignificant lost item, it can be taken possession of without announcement. The announcement of the lost item should be made by saying, "Whose money has been lost?" without specifying the item, for fear that someone might falsely claim it. If the finder takes possession of the lost item after a year and then its owner appears, the finder has the option to let the owner choose between confirming the charitable donation (if the finder had given it away in charity) or returning the money to them.