Reference: at-Tabaraanee in al-Awsat; Mabaahith fee Ahkaam al-Fatwa – Page 7
Jaabir ibn ‘Abdullaah al-Ansaaree narrated that the Messenger of Allaah ﷺ said:
It is not befitting for a scholar to remain silent upon his knowledge, and nor is it befitting for one who is ignorant to remain silent upon his ignorance.