"So they," by that book, "are holding fast," using it to argue with Us. That is: We have not given them any book containing what they claim.
﴿فهم﴾ بذلك الْكتاب ﴿مستمسكون﴾ يحاجوننا بِهِ أَي: لم نؤتهم كتابا فِيهِ مَا يَقُولُونَ
