It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Everything has a mine (source), and the mine of piety (taqwa) is the hearts of those who have knowledge (of Allah)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13128