{"But Yusuf kept it within himself and did not reveal it to them"}1. Meaning: he did not reveal the reality of the Cloaking (al-talbis) that he manifested by his saying to them: {"You are in a worse position, and God is most knowing of what you describe"}2. The "Position" (makan) here is the town they were in; the blame is directed at the town, not at them.
So he said: "You are in a worse position," meaning: you are residing in a most evil place, as a disparagement of the town, not them; and God knows best what they describe of him in terms of incapacity and cloaking.
Then they reinforced and completed that by their saying to him: {They said, "O Aziz, indeed he has a father, a very old man, so take one of us in his place. Indeed, we see you as one of the doers of good." ❁ He said, "[God] forbid that we should take except him with whom we found our possession. Indeed, we would then be wrongdoers." ❁ So when they had despaired of him, they secluded themselves in private consultation. Their eldest said, "Do you not know that your father has taken from you a pledge by God and how you failed before concerning Yusuf? So I will never leave the land until my father permits me or God decides for me; and He is the best of judges"}3. That is, when they despaired of Benjamin—which was the interval (fatra) during which they held that the judgment belongs to God—it means they knew the affair was close to Disclosure (al-kashf), so they became free from Dissimulation (taqiyya) and were saved from it.
And the words of the Mighty and Sublime: {"Do you not know that your father has taken from you a pledge by God... So I will never leave the land until my father permits me or God decides for me; and He is the best of judges"}4.