Musannaf Ibn Abi Shayba 33:136

Ibn Numayr narrated to us, he said: Hisham narrated to us, from al-Hasan, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Knowledge is of two types: knowledge in the heart, and that is the beneficial knowledge; and knowledge upon the tongue, and that is Allah’s proof against His servants."