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  

'Umar reported me to collect the sadaqah (i.e. zakat). When I became free, he ordered to give me payment for it. I said: I have worked for the sake of Allah. He said: Take what you have been given, for I held an administrative post in the time of the Messenger of Allah ﷺ, and he gave me payment for it.  

اسْتَعْمَلَنِي عُمَرُ عَلَى الصَّدَقَةِ فَلَمَّا فَرَغْتُ أَمَرَ لِي بِعُمَالَةٍ فَقُلْتُ إِنَّمَا عَمِلْتُ لِلَّهِ قَالَ خُذْ مَا أُعْطِيتَ فَإِنِّي قَدْ عَمِلْتُ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ فَعَمَّلَنِي  

Al-Mustawrid heard the Prophet ﷺ say: He who acts as an employee for us must get a wife; if he has not a servant, he must get one, and if he has not a dwelling, he must get one. He said that Abu Bakr reported: I was told that the Prophet ﷺ said: He who takes anything else he is unfaithful or thief.  

سَمِعْتُ النَّبِيَّ ﷺ يَقُولُ مَنْ كَانَ لَنَا عَامِلاً فَلْيَكْتَسِبْ زَوْجَةً فَإِنْ لَمْ يَكُنْ لَهُ خَادِمٌ فَلْيَكْتَسِبْ خَادِمًا فَإِنْ لَمْ يَكُنْ لَهُ مَسْكَنٌ فَلْيَكْتَسِبْ مَسْكَنًا قَالَ قَالَ أَبُو بَكْرٍ أُخْبِرْتُ أَنَّ النَّبِيَّ ﷺ قَالَ مَنِ اتَّخَذَ غَيْرَ ذَلِكَ فَهُوَ غَالٌّ أَوْ سَارِقٌ