COMMENTARY on 12:77
Mustafa Khattab:

Translation:
˹To distance themselves,˺ Joseph’s brothers argued, “If he has stolen, so did his ˹full˺ brother before.”18 But Joseph suppressed his outrage—revealing nothing to them—and said ˹to himself˺, “You are in such an evil position,18 and Allah knows best ˹the truth of˺ what you claim.”
Commentary:
18   Joseph was falsely accused of theft when he was young.

 

A. Yusuf Ali:

Translation:
They said: "If he steals, there was a brother of his who did steal before (him)." 1747 But these things did Joseph keep locked in his heart, revealing not the secrets to them. 1748 He (simply) said (to himself): "You are the worse situated; 1749 and Allah knoweth best the truth of what you assert!"
Commentary:

1747  The hatred of the ten for Joseph and Benjamin comes out again. They are not only ready to believe evil of Benjamin, but they carry their thoughts back to Joseph and call him a thief as well. They had injured Joseph; and by a false charge of this kind they salve their conscience. Little did they suspect that Joseph was before them, under another guise, and their falsehood and treachery, would soon be exposed.

1748  There were many secrets: (1) that he was Joseph himself; (2) that his brother, Benjamin, knew him; (3) that there was no guilt in Benjamin, but the whole practical joke was in furtherance of a great plan (see n. 1745 above); (4) that they were giving themselves away, and were unconsciously facilitating the plan, though their motives were not aboveboard.

1749  "Ah!" thought Joseph, "you think that Benjamin is safely out of the way, and that Joseph was got rid of long since! Would you be surprised to know that you have given yourselves away, that you are now in the power of Joseph, and that Joseph is the very instrument of your exposure and (let us hope) of your repentance?"

 

Muhammad Asad:

Translation:
[As soon as the cup came to light out of Benjamin's bag, the brothers] exclaimed: "If he has stolen-well, a brother of his used to steal afore-time !" 78 Thereupon Joseph said to himself, without revealing his thought to them: 79 "You are far worse in this respect, and God is fully aware of what you are saying. 80
Commentary:
78  The reference is obviously to Benjamin's full brother, Joseph. In the absence of any indication that the latter had ever before been accused of theft, it is reasonable to assume that the brothers, unaware of the fact that they were standing before Joseph, simply wanted to vilify him in order to dissociate themselves more effectively from Benjamin, who now appeared to have been convicted of theft.
79  Lit ., "Joseph concealed it within himself and did not reveal it to them; he said. . .", etc. According to almost all the commentators, the pronoun "it" refers to Joseph's subsequent "saying" or, rather, thought, indicated by the verb "he said" (i.e., within himself); hence my free rendering of this phrase.
80  Lit., "of what you attribute", i.e., to Joseph and Benjamin-sc., "since you yourselves have stolen Joseph from his father".