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
darimi:367 – Muḥammad b. Ḥumayd > Mihrān > Abū Sinān > Abū Isḥāq > ʿAmr b. Maymūn

[Machine] "Umar's knowledge decreased by two thirds," I said to Ibrahim. He replied, "Umar's knowledge decreased by nine tenths."  

الدارمي:٣٦٧ – أَخْبَرَنَا مُحَمَّدُ بْنُ حُمَيْدٍ حَدَّثَنَا مِهْرَانُ حَدَّثَنَا أَبُو سِنَانٍ عَنْ أَبِي إِسْحَاقَ عَنْ عَمْرِو بْنِ مَيْمُونٍ قَالَ

«ذَهَبَ عُمَرُ بِثُلُثَيِ الْعِلْمِ» قَالَ فَذَكَرْتُ لِإِبْرَاهِيمَ فَقَالَ «ذَهَبَ عُمَرُ بِتِسْعَةِ أَعْشَارِ الْعِلْمِ»