Tafseer Ibn Kathir of AL MU'MIN [84]

فَلَمَّا رَأَوْا بَأْسَنَا قَالُوا آمَنَّا بِاللَّهِ وَحْدَهُ وَكَفَرْنَا بِمَا كُنَّا بِهِ مُشْرِكِينَ

And when they saw Our punishment, they said," We believe in Allah alone and disbelieve in that which we used to associate with Him."