Sura al-Fatḥ 48:10

إِنَّ ٱلَّذِينَ يُبَايِعُونَكَ إِنَّمَا يُبَايِعُونَ ٱللَّـهَ يَدُ ٱللَّـهِ فَوْقَ أَيْدِيهِمْ فَمَن نَّكَثَ فَإِنَّمَا يَنكُثُ عَلَىٰ نَفْسِهِۦ وَمَنْ أَوْفَىٰ بِمَا عَٰهَدَ عَلَيْهُ ٱللَّـهَ فَسَيُؤْتِيهِ أَجْرًا عَظِيمًا

inna lladhīna yubāyiʿūnaka innamā yubāyiʿūna allāha yadu allāhi fawqa aydīhim fa-man nakatha fa-innamā yankuthu ʿalā nafsihi wa-man awfā bi-mā ʿāhada ʿalayhu allāha fa-sa-yuʾtīhi ajran ʿaẓīman

Verily those who plight their fealty to thee do no less than plight their fealty to Allah: the Hand of Allah is over their hands: then any one who violates his oath, does so to the harm of his own soul, and any one who fulfils what he has covenanted with Allah,- Allah will soon grant him a great Reward.