It is narrated from Sayyiduna Umar bin Malik al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "I command you with three things and forbid you from three things: I command you not to associate anything with Allah, to hold fast together to obedience until the command of Allah comes to you while you are in that state, and to give sincere counsel to those in authority who command you with the command of Allah. And I forbid 'it is said' and 'he said' (idle talk), excessive questioning, and wasting wealth.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8276