From Sahih Muslim (Hadith 158):
It is narrated on the authority of 'Imran b. Husain that the Prophet (may peace and blessings be upon him) said:Modesty brings forth nothing but goodness. Bushair b. Ka'b said: It is recorded in the books of wisdom, there lies sobriety in it and calmness of mind in it, Imran said: I am narrating to you the tradition of the Messenger of Allah (may peace and blessings be upon him) and you talk of your books
Reference: Muslim 158