مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 265
Knowledge
Chapter - Section 3
وَعَنِ الْأَعْمَشِ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «آفَةُ الْعِلْمِ النِّسْيَانُ وَإِضَاعَتُهُ أَنْ تُحَدِّثَ بِهِ غَيْرَ أَهْلِهِ» . رَوَاهُ الدَّارِمِيُّ مُرْسلا
Al-A‘mash reported God’s messenger as saying, "The calamity which affects knowledge is forgetfulness, and wasting it is to convey it to those who are unworthy of it.” Darimi transmitted it in mursal form.
Mishkat al-Masabih, 265ضَعِيف (الألباني)