It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever is asked about some knowledge and conceals it will be bridled with a bridle of fire on the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13630