 to keep their established covenants with god not to disregard their firm oaths they have already appointed god as their guarantor. god certainly knows what you do.
وأوفوا بعهد الله إذا عاهدتم ولا تنقضوا الأيمان بعد توكيدها وقد جعلتم الله عليكم كفيلا إن الله يعلم ما تفعلون