2. O ye who believe! raise not your voices above the voice of the Prophet nor speak aloud to him in talk as ye may speak aloud to one another lest your deeds become vain and ye perceive not.

Notes (Tafseer)

4920. It is bad manners to talk loudly before your Leader. Some ill-mannered people so raise their voices as to drown the voice of their Leader, in conversation or in Council.

4921. Such rudeness may even destroy the value of such services as they may otherwise have been able to render, and all this without their even realising the harm they were doing to the Cause.