قَالَ هَلْ ءَامَنُكُمْ عَلَيْهِ إِلَّا كَمَآ أَمِنتُكُمْ عَلَىٰٓ أَخِيهِ مِن قَبْلُ ۖ فَٱللَّهُ خَيْرٌ حَٰفِظًا ۖ وَهُوَ أَرْحَمُ ٱلرَّٰحِمِينَ

Joseph probably felt that it was discourteous to take the price of the corn from his brothers, or he perhaps thought that a lack of money might prevent them from coming back again. Therefore, he instructed his men that whatever amount his brothers had paid towards the corn should be quietly put among their belongings, so that when they went home and opened their bundles, they would find it and come again with their brother, Benjamin. Jacob, on the one hand, expressed his lack of trust in his sons where Benjamin was concerned. On the other hand, he also said that neither they nor anybody else had any power. Whatever God wished was bound to happen. But this happening is caused by human hands, so that an evil person, by performing evil deeds, may lay bare the truth about himself, while the good person, by performing righteous deeds, may have his name listed among the righteous.

— Source: Tazkirul Quran (Maulana Wahiduddin Khan) via Quran.com (12:64)