Quran 16:91 from Surah An-Nahl on Divine Marvels.
وَأَوۡفُواْ بِعَهۡدِ ٱللَّهِ إِذَا عَٰهَدتُّمۡ وَلَا تَنقُضُواْ ٱلۡأَيۡمَٰنَ بَعۡدَ تَوۡكِيدِهَا وَقَدۡ جَعَلۡتُمُ ٱللَّهَ عَلَيۡكُمۡ كَفِيلًاۚ إِنَّ ٱللَّهَ يَعۡلَمُ مَا تَفۡعَلُونَ
English translation: And fulfil the covenant (of) Allah when you have taken a covenant and (do) not break oaths after their confirmation while verily you have made Allah over you a surety Indeed Allah knows what you do
Transliteration: wa-awfu bi'ahdi al-lahi idha ahadttum wala tanqudu al-aymana ba'da tawkidiha waqad ja'altumu al-laha alaykum kafilan inna al-laha ya'lamu ma taf 'aluna