The Prophet ﷺ as saying: When we appoint someone to an administrative post and provide him with an allowance, anything he takes beyond that is unfaithful dealing.
عَنِ النَّبِيِّ ﷺ قَالَ مَنِ اسْتَعْمَلْنَاهُ عَلَى عَمَلٍ فَرَزَقْنَاهُ رِزْقًا فَمَا أَخَذَ بَعْدَ ذَلِكَ فَهُوَ غُلُولٌ