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.
darimi:388Yaʿlá > al-Masʿūdī > al-Qāsim

[Machine] To me, Abdullah says,"Verily, I reckon that a man forgetting knowledge that he knew is a sin that he commits."  

الدارمي:٣٨٨أَخْبَرَنَا يَعْلَى حَدَّثَنَا الْمَسْعُودِيُّ عَنِ الْقَاسِمِ قَالَ قَالَ

لِي عَبْدُ اللَّهِ «إِنِّي لَأَحْسَبُ الرَّجُلَ يَنْسَى الْعِلْمَ كَانَ يَعْلَمُهُ لِلْخَطِيئَةِ كَانَ يَعْمَلُهَا»  


See similar narrations below:

Collected by Ṭabarānī, Aḥmad's Zuhd
tabarani:8930ʿAlī b. ʿAbd al-ʿAzīz > Abū Nuʿaym > al-Masʿūdī > al-Qāsim

[Machine] Abdullah: "Verily, I believe that a person forgets knowledge whenever they commit a sin that they have learned."  

الطبراني:٨٩٣٠حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ الْعَزِيزِ ثنا أَبُو نُعَيْمٍ ثنا الْمَسْعُودِيُّ عَنِ الْقَاسِمِ قَالَ

عَبْدُ اللهِ «إِنِّي لَأَحْسِبُ الرَّجُلَ يَنْسَى الْعِلْمَ كُلَّمَا يَعْلَمُهُ الْخَطِيئَةَ يَعْمَلُهَا»  

ahmad-zuhd:853ʿAbdullāh from my father > Wakīʿ > al-Masʿūdī > al-Qāsim b. ʿAbd al-Raḥman Wa-al-Ḥasan b. Saʿd

[Machine] "Abdullah, I believe that a person who forgets knowledge that he once possessed, commits a mistake."  

الزهد لأحمد:٨٥٣حَدَّثَنَا عَبْدُ اللَّهِ حَدَّثَنَا أَبِي حَدَّثَنَا وَكِيعٌ حَدَّثَنَا الْمَسْعُودِيُّ عَنِ الْقَاسِمِ بْنِ عَبْدِ الرَّحْمَنِ وَالْحَسَنِ بْنِ سَعْدٍ قَالَ

عَبْدُ اللَّهِ إِنِّي لَأَحْسَبُ الرَّجُلَ يَنْسَى الْعِلْمَ كَانَ يَعْلَمُهُ بِالْخَطِيئَةِ يَعْمَلُهَا