Quran 16:91 An-Nahl, ayah 91 of 128

وَأَوْفُوا۟ بِعَهْدِ ٱللَّهِ إِذَا عَـٰهَدتُّمْ وَلَا تَنقُضُوا۟ ٱلْأَيْمَـٰنَ بَعْدَ تَوْكِيدِهَا وَقَدْ جَعَلْتُمُ ٱللَّهَ عَلَيْكُمْ كَفِيلًا ۚ إِنَّ ٱللَّهَ يَعْلَمُ مَا تَفْعَلُونَ ۝٩١

16:91 Fulfil the covenant of Allah when ye have covenanted, and break not your oaths after the asseveration of them, and after ye have made Allah surety over you. Lo! Allah knoweth what ye do.