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:37:84 –

When he came to his Lord with a sound heart  

When he came to his Lord, in other words, he continued to follow Him upon coming to Him, with a heart that was pure, of any doubt or the like,
القرآن:٣٧:٨٤ –

إِذْ جَاءَ رَبَّهُ بِقَلْبٍ سَلِيمٍ  

{إذ جاء ربهَّ} أي تابعه وقت مجيئه {بقلب سليم} من الشك وغيره.