﴿ أَوَكُلَّمَا عَٰهَدُوا۟ عَهْدًۭا نَّبَذَهُۥ فَرِيقٌۭ مِّنْهُم ۚ بَلْ أَكْثَرُهُمْ لَا يُؤْمِنُونَ ﴾

“Is it not so that every time they made a promise [unto God], some of them cast it aside? Nay, indeed: most of them do not believe.”

(Is it ever so that when they make a covenant) i.e. the Jewish leaders with Muhammad (a party of them set it aside?) reject and break it. (The truth is, most of them) all of them in fact (believe not).