Surat Al-Fath (The Victory) - الفتح

إِنَّ ٱلَّذِينَ يُبَايِعُونَكَ إِنَّمَا يُبَايِعُونَ ٱللَّهَ يَدُ ٱللَّهِ فَوْقَ أَيْدِيهِمْ فَمَن نَّكَثَ فَإِنَّمَا يَنكُثُ عَلَىٰ نَفْسِهِۦ وَمَنْ أَوْفَىٰ بِمَا عَٰهَدَ عَلَيْهُ ٱللَّهَ فَسَيُؤْتِيهِ أَجْرًا عَظِيمًا ﴿١٠﴾

Surely those who swear allegiance to you do but swear allegiance to Allah; the hand of Allah is above their hands. Therefore whoever breaks (his faith), he breaks it only to the injury of his own soul, and whoever fulfills what he has covenanted with Allah, He will grant him a mighty reward.