فَلَمّا رَجَعوا إِلىٰ أَبيهِم قالوا يا أَبانا مُنِعَ مِنَّا الكَيلُ فَأَرسِل مَعَنا أَخانا نَكتَل وَإِنّا لَهُ لَحافِظونَ

So when they returned to their father, they said, "O our father, [further] measure has been denied to us, so send with us our brother [that] we will be given measure. And indeed, we will be his guardians."