The Quran

ارجِعوا إِلىٰ أَبيكُم فَقولوا يا أَبانا إِنَّ ابنَكَ سَرَقَ وَما شَهِدنا إِلّا بِما عَلِمنا وَما كُنّا لِلغَيبِ حافِظينَ

Muhammad Asad

[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;¹ 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.²

I.e., the finding of the King's cup in Benjamin's bag (Baghawi and Zamakhshari).
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).