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
tabarani:13142 – Yūsuf al-Qāḍī > Muḥammad b. Abū Bakr al-Muqaddamī > Bishr b. Manṣūr > ʿAbd al-Raḥman b. Isḥāq > al-Zuhrī > Sālim > Ibn ʿUmar

[Machine] The Prophet's ﷺ strongest belief was "No, but it is the turner of hearts."  

الطبراني:١٣١٤٢ – حَدَّثَنَا يُوسُفُ الْقَاضِي ثنا مُحَمَّدُ بْنُ أَبِي بَكْرٍ الْمُقَدَّمِيُّ ثنا بِشْرُ بْنُ مَنْصُورٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ إِسْحَاقَ عَنِ الزُّهْرِيِّ عَنْ سَالِمٍ عَنِ ابْنِ عُمَرَ قَالَ

كَانَتْ أَكْثَرُ أَيْمَانِ النَّبِيِّ ﷺ «لَا وَمُصَرِّفِ الْقُلُوبِ»  

See similar narrations below:

Collected by Nasāʾī, Ibn Mājah
nasai:3762 – Muḥammad b. Yaḥyá b. ʿAbdullāh > Muḥammad b. al-Ṣalt Abū Yaʿlá > ʿAbdullāh b. Rajāʾ > ʿAbbād b. Isḥāq > al-Zuhrī > Sālim from his father

"The oath by which the Messenger of Allah used to swear was: 'No, by the Controller of the hearts.'"  

النسائي:٣٧٦٢ – أَخْبَرَنِي مُحَمَّدُ بْنُ يَحْيَى بْنِ عَبْدِ اللَّهِ قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ الصَّلْتِ أَبُو يَعْلَى قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ رَجَاءٍ عَنْ عَبَّادِ بْنِ إِسْحَاقَ عَنِ الزُّهْرِيِّ عَنْ سَالِمٍ عَنْ أَبِيهِ قَالَ

كَانَتْ يَمِينُ رَسُولِ اللَّهِ ﷺ الَّتِي يَحْلِفُ بِهَا لاَ وَمُصَرِّفِ الْقُلُوبِ  

ibnmajah:2092 – Abū Isḥāq al-Shāfiʿī Ibrāhīm b. Muḥammad b. al-ʿAbbās > ʿAbdullāh b. Rajāʾ al-Makkī > ʿAbbād b. Isḥāq > Ibn Shihāb > Sālim from his father

"The swearing most frequently sworn by the Messenger of Allah ﷺ was: 'No, by the Controller of the hearts."'  

ابن ماجة:٢٠٩٢ – حَدَّثَنَا أَبُو إِسْحَاقَ الشَّافِعِيُّ إِبْرَاهِيمُ بْنُ مُحَمَّدِ بْنِ الْعَبَّاسِ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ رَجَاءٍ الْمَكِّيُّ عَنْ عَبَّادِ بْنِ إِسْحَاقَ عَنِ ابْنِ شِهَابٍ عَنْ سَالِمٍ عَنْ أَبِيهِ قَالَ

كَانَتْ أَكْثَرُ أَيْمَانِ رَسُولِ اللَّهِ ﷺ لاَ وَمُصَرِّفِ الْقُلُوبِ