Word by Word Analysis

وَأَوْفُوا۟ بِعَهْدِ ٱللَّهِ إِذَا عَـٰهَدتُّمْ وَلَا تَنقُضُوا۟ ٱلْأَيْمَـٰنَ بَعْدَ تَوْكِيدِهَا وَقَدْ جَعَلْتُمُ ٱللَّهَ عَلَيْكُمْ كَفِيلًا ۚ إِنَّ ٱللَّهَ يَعْلَمُ مَا تَفْعَلُونَ 91

And fulfill the covenant of Allāh when you have taken it, [O believers], and do not break oaths after their confirmation while you have made Allāh, over you, a security [i.e., witness]. Indeed, Allāh knows what you do.