COMMENTARY on 12:81
Mustafa Khattab:

Translation:
Return to your father and say, ‘O our father! Your son committed theft. We testify only to what we know. We could not guard against the unforeseen.19
Commentary:
19   We did not know when we gave you our solemn oath that our brother was going to steal.

 

A. Yusuf Ali:

Translation:
"Turn you back to your father, and say, ´O our father! behold! your son committed theft! we bear witness only to what we know, and we could not well guard against the unseen! 1754
Commentary:

1754  'He stole in secret and without our knowledge. How could we in the circumstances prevent it? 1 This may have been a good statement for the other nine brothers, but Judah was himself personally and specially pledged.

 

Muhammad Asad:

Translation:
[And as for you others,] return to your father and say: `O our father! Behold, thy son has stolen-but we [can] bear witness to no more than what has become known to us; 83 and [although we gave you our pledge,] we could not guard against something that [lay hidden in the future and, hence,] was beyond the reach of our perception. 84
Commentary:
83  I.e., the finding of the King's cup in Benjamin's bag (Baghawi and Zamakhshari).
84  Lit., "We were not guardians over that which was beyond the reach of [our] perception": i.e., "at the time when we gave you our pledge regarding Benjamin; we did not know that he would steal" (Zamakhshari).