Surah As-Saf 61:3

كَبُرَ مَقْتًا عِندَ ٱللَّهِ أَن تَقُولُوا۟ مَا لَا تَفْعَلُونَ

Greatly hateful in the sight of Allāh is that you say what you do not do.

Translation: Saheeh International

Tafsir

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.

Excerpt from Tafsir al-Jalalayn, commentary on 61:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.