التفسير التبليغي
(He) said: "Allah forbid that we should take other than him with whom we found our property. Indeed, we would then be wrongdoers." (79)
Yusuf (peace be upon him) seeks refuge in Allah from taking anyone other than the one in whose luggage the king's measuring cup was found. What is his sin in this matter? And no one can be punished for a sin committed by another.
(He) said: "Allah forbid" - meaning, we seek refuge in Allah the Almighty.
(He) said: "Allah forbid" - meaning, we seek refuge in Allah from acquitting a guilty person and convicting an innocent one, thus taking an innocent person for the sin of the wrongdoer.
Yusuf (peace be upon him) did not reveal his true identity to them because he did not perceive signs of repentance and remorse from them.
His intention in detaining his brother was not to seek revenge on his brothers.
When he took his brother, he wanted to observe the state of their hearts.
He feared that if he detained him without cause, it would increase his father's grief upon his existing grief, so he fabricated the incident of the measuring cup.
"Except him" - meaning the person "with whom we found our property," and he did not say: "stole our property."
"Except him with whom we found our property," and he did not say: "except him who stole our property."
"Indeed, we would then" - meaning, if we were to take someone other than the one with whom we found our property, even with his consent - "be wrongdoers."
It is not permissible for him to wrong anyone, or to take someone for the crime of another.
"Indeed, we would then be wrongdoers" - meaning, we resort to Allah to protect us from taking someone whom we have no right to take; that is, to protect us from injustice.
Yusuf's (peace be upon him) response has an inner meaning, which is that Allah Almighty commanded him by revelation to take Benjamin for purposes that He (Glorified be He) knew in that, so if he had taken someone else, he would have been unjust to himself and acting contrary to the revelation.
Source: التفسير التبليغي