His statement: 'The believers are only those who, when Allah is mentioned, feel a fear in their hearts,' meaning: they soften out of fear.
قَوْلُهُ: ﴿إِنَّمَا الْمُؤْمِنُونَ الَّذِينَ إِذَا ذكر الله وجلت قُلُوبهم﴾ أَيْ: رَقَّتْ مَخَافَةَ