Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:36:11 –

You can only warn one who follows the message and fears the Most Merciful unseen. So give him good tidings of forgiveness and noble 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.
القرآن:٣٦:١١ –

إِنَّمَا تُنْذِرُ مَنِ اتَّبَعَ الذِّكْرَ وَخَشِيَ الرَّحْمَٰنَ بِالْغَيْبِ ۖ فَبَشِّرْهُ بِمَغْفِرَةٍ وَأَجْرٍ كَرِيمٍ  

{إنما تنذر} ينفع إنذارك {من أتَّبع الذكر} القرآن {وخشي الرحمن بالغيب} خافه ولم يره {فبشّره بمغفرة وأجر كريم} هو الجنة.