It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Holy Prophet (peace and blessings of Allah be upon him) said: If a person is asked about knowledge and he conceals it without any reason, then on the Day of Resurrection a bridle of fire will be put in his mouth.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10420
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن