Musnad Ahmad 763
It was narrated from Muhammad bin `Ali that he heard `Ali bin Abi Talib       (رضي الله عنه) say:
The Messenger of Allah (ﷺ) said: “I have been given that which was not given to any of the other Prophet (ﷺ).” We said: O Messenger of Allah (ﷺ), what is it? He said: “I have been supported (against the enemy) with fear, 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.`
حَدَّثَنَا عَبْدُ الرَّحْمَنِ، حَدَّثَنَا زُهَيْرٌ، عَنْ عَبْدِ اللَّهِ يَعْنِي ابْنَ مُحَمَّدِ بْنِ عَقِيلٍ، عَنْ مُحَمَّدِ بْنِ عَلِيٍّ، أَنَّهُ سَمِعَ عَلِيَّ بْنَ أَبِي طَالِبٍ، رَضِيَ اللَّهُ عَنْهُ يَقُولُ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أُعْطِيتُ مَا لَمْ يُعْطَ أَحَدٌ مِنْ الْأَنْبِيَاءِ فَقُلْنَا يَا رَسُولَ اللَّهِ مَا هُوَ قَالَ نُصِرْتُ بِالرُّعْبِ وَأُعْطِيتُ مَفَاتِيحَ الْأَرْضِ وَسُمِّيتُ أَحْمَدَ وَجُعِلَ التُّرَابُ لِي طَهُورًا وَجُعِلَتْ أُمَّتِي خَيْرَ الْأُمَمِ‏.‏