You Will Tell Them One Day

They threw him into a well. Then they took his shirt, slaughtered a small goat, and poured the goat's blood over the shirt. Then they went back to their father, crying, and said: our father, the wolf ate him. He had told them he was afraid a wolf would eat him — so they said, fine: let us say that a wolf ate him.

So when they took him away, they all agreed to throw him down to the bottom of the well. As they were throwing him into the well, Allah (swt) revealed to Yūsuf: and We inspired him — you will surely one day inform them of this affair of theirs, while they do not realise who you are. Allah (swt) told Yūsuf that one day he would tell his brothers about this event, and they would not know that it was he who was speaking to them. Allah was telling Yūsuf of something, but Yūsuf did not know its details, or when it would happen. It was a prophecy that Allah (swt) inspired in Yūsuf.