Zayd bin Sallam narrates from his grandfather that Amir Mu'awiyah (may Allah be pleased with him) wrote to Abd al-Rahman bin Shibl (may Allah be pleased with him) asking him to teach the people what he had heard from the Messenger of Allah (peace and blessings be upon him). So Abd al-Rahman (may Allah be pleased with him) gathered them and said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Learn the Qur'an, and when you have learned it, do not go to extremes in it (do not exceed the limits), do not turn away from it, do not make it a means of earning your food, and do not use it to seek more for yourselves." Then he mentioned the complete hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2270