The Noble Qur'an

إِذْ جَعَلَ الَّذِينَ كَفَرُوا فِي قُلُوبِهِمُ الْحَمِيَّةَ حَمِيَّةَ الْجَاهِلِيَّةِ فَأَنزَلَ اللَّهُ سَكِينَتَهُ عَلَى رَسُولِهِ وَعَلَى الْمُؤْمِنِينَ وَأَلْزَمَهُمْ كَلِمَةَ التَّقْوَى وَكَانُوا أَحَقَّ بِهَا وَأَهْلَهَا وَكَانَ اللَّهُ بِكُلِّ شَيْءٍ عَلِيماً   

48.26 . When those who disbelieve had set up in their hearts zealotry , the zealotry of the Age of Ignorance , then Allah sent down His peace of reassurance upon His messenger and upon the believers and imposed on them the word of self restraint , for they were worthy of it and meet for it . And Allah is Aware of all things .