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
ahmad-zuhd:1806 – ʿAbdullāh > Abū Maʿmar > Sufyān

[Machine] Abu Ja'far said, "Certainty is fleeting thoughts while faith is steadfast in the heart."  

الزهد لأحمد:١٨٠٦ – حَدَّثَنَا عَبْدُ اللَّهِ حَدَّثَنِي أَبُو مَعْمَرٍ عَنْ سُفْيَانَ قَالَ

أَبُو جَعْفَرٍ «الْيَقِينُ خَطَرَاتٌ وَالْإِيمَانُ ثَابِتٌ فِي الْقَلْبِ»  

See similar narrations below:

Collected by Suyūṭī