Surah As-Saffat, ayah 29

37:29

قَالُواْ بَل لَّمۡ تَكُونُواْ مُؤۡمِنِينَ ٢٩

Qālū bal lam takūnū mu'minīn

They [i.e., the oppressors] will say, "Rather, you [yourselves] were not believers,