وَعَنْ سُفْيَانَ أَنَّ عُمَرَ بْنَ الْخَطَّابِ رَضِيَ اللَّهُ عَنْهُ
قَالَ لِكَعْبٍ: مَنْ أَرْبَابُ الْعِلْمِ؟ قَالَ: الَّذِي يَعْمَلُونَ بِمَا يَعْلَمُونَ. قَالَ: فَمَا أَخْرَجَ الْعِلْمَ مِنْ قُلُوبِ الْعُلَمَاءِ؟ قَالَ الطَّمَعُ
Umar ibn al-Khattab asked Kab who were the lords of knowledge, and he replied that they are those who act according to what they know. He then asked what it is that takes knowledge from the hearts of the learned and was told that it is covetousness.
Mishkat al-Masabih 251, Book 3, Knowledge, Hadith 62. 1 min read