because of their breaking the covenant and their rejecting the ayat of allah and their killing the prophets unjustly and their saying our hearts are ghulf nay allah has set a seal upon their hearts because of their disbelief so they believe not but a little.
فبما نقضهم ميثاقهم وكفرهم بآيات الله وقتلهم الأنبياء بغير حق وقولهم قلوبنا غلف بل طبع الله عليها بكفرهم فلا يؤمنون إلا قليلا