Muhammad bin Ishaq narrated from his uncle Musa bin Yasar: It has reached me that Sayyiduna Salman (may Allah be pleased with him) wrote to Sayyiduna Abu Darda (may Allah be pleased with him): Knowledge is like springs upon which people come, and all of them draw from it, and many people benefit from it. And a hadith of wisdom that is not conveyed is like a body without a soul, and knowledge that is not spread is like a treasure from which nothing is spent. The example of a scholar is like that of a man who placed a lamp on a dark path, from which every passerby receives light, and every person prays good for him.