'Atiyya ibn 'Urwa as-Sa'di, the Companion, said, "The Messenger of Allah, may Allah bless him and grant him peace, said, 'The slave [of Allah] will not achieve the status of being one of the Godfearing until he leaves what does not concern him out of consideration for what does concern him."

Riyadh-as-Saliheen by Imam Al-Nawawi, volume 4, hadith number 596 - Sunni Hadith