Tirmidhi

"Abu'd-Darda' (may Allah be pleased with him) said, "I heard the Messenger of Allah (may Allah bless him and grant him peace), say, 'Allah will make the path to the Garden easy for anyone who travels a path in search of knowledge. Angels spread their wings for the seeker of knowledge out of pleasure for what he is doing. Everyone in the heavens and everyone in the earth ask forgiveness for a man of knowledge, even the fish in the water. The superiority of the man of knowledge to the man of worship is like the superiority of the moon to all the planets. The men of knowledge are the heirs of the Prophets. The Prophets bequeath neither dinar nor dirham; they bequeath knowledge. Whoever takes it has taken an ample portion.'" [Related by Abu Dawud and Tirmidhi; Riyad al-Salihin: 1388]"