جامع الترمذي

Narrated Umayyah: that she asked 'Aishah about the saying of Allah, blessed and Most High: And whether you disclose what is in yourselves or conceal it, Allah will call you to account for it (2:284). And about His saying: And whoever does evil, he will be recompensed for it (4:123). She said: "No one has asked me about it since I asked the Messenger of Allah (ﷺ), he said: 'This is Allah's admonition for His slave regarding whatever he is stricken with, of fever and problems, even the item that he has in the pocket of his shirt which he loses and worries about, until the slave's sins are removed, just as the red ore is removed from the bellows.'"