Musnad Ahmad 1361

It was narrated Muhammad bin Ali al-Akbar that he heard his father Ali bin Abi Talib (رضي الله عنه) say: The Messenger of Allah (ﷺ) said: "I have been given four thing that which was not given to any of the other Prophets.” I have been given the keys of the Earth, I have been named Ahmad, the dust has been made a means of purification for me and my ummah has been made the best of nations."