Surah As-Saff, ayah 3

كَبُرَ مَقۡتًا عِندَ ٱللَّهِ أَن تَقُولُواْ مَا لَا تَفۡعَلُونَ ٣

Kabura maqtan 'indallāhi an taqūlū mā lā taf'alūn

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