﴿ إِنَّمَا تُنذِرُ مَنِ ٱتَّبَعَ ٱلذِّكْرَ وَخَشِىَ ٱلرَّحْمَٰنَ بِٱلْغَيْبِ ۖ فَبَشِّرْهُ بِمَغْفِرَةٍۢ وَأَجْرٍۢ كَرِيمٍ ﴾

“Thou canst [truly] warn only him who is willing to take the reminder to heart, and who stands in awe of the Most Gracious although He is beyond the reach of human perception: unto such, then, give the glad tiding of [God’s] forgiveness and of a most excellent reward!”

You can only warn in other words your warning will only benefit him who follows the Remembrance the Qur’ān and fears the Compassionate One in secret who fears Him despite not having seen Him; so give him the good tidings of forgiveness and a noble reward namely Paradise.