It was narrated that Kathir bin Qais said:
"I was sitting with Abu Darda' in the mosque of Damascus when a man came to him and said: 'O Abu Darda', I have come to you from Al-Madinah, the city of the Messenger of Allah, for a Hadith which I have heard that you narrate from the Prophet.' He said: 'Did you not come for trade?' He said: 'No.' He said: 'Did you not come for anything else?' He said: 'No.' He said: 'I heard the Messenger of Allah say: "Whoever follows a path in the pursuit of knowledge, Allah will make easy for him a path to Paradise. The angels lower their wings in approval of the seeker of knowledge, and everyone in the heavens and on earth prays for forgiveness for the seeker of knowledge, even the fish in the sea. The superiority of the scholar over the worshipper is like the superiority of the moon above all other heavenly bodies. The scholars are the heirs of the Prophets, for the Prophets did not leave behind a Dinar or Dirham, rather they left behind knowledge, so whoever takes it has taken a great share.'"
English reference: Vol. 1, Book 1, Hadith 223
Arabic reference: Book 1, Hadith 228