﴿ كَبُرَ مَقْتًا عِندَ ٱللَّهِ أَن تَقُولُوا۟ مَا لَا تَفْعَلُونَ ﴾

“Most loathsome is it in the sight of God that you say what you do not do!”

It is greatly loathsome maqtan is for specification to God that you say an taqūlū constitutes the agent of the verb kabura ‘it is greatly’ what you do not do.