Abu Dawud Book 36, Hadith Number 4865.

Chapter : Not known.

Narated By Mu’adh ibn Anas : The Prophet (PBUH) said: If anyone guards a believer from a hypocrite, Allah will send an angel who will guard his flesh on the Day of Resurrection from the fire of Jahannam; but if anyone attacks a Muslim saying something by which he wishes to disgrace him, he will be restrained by Allah on the bridge over Jahannam till he is acquitted of what he said.