Shiavault - a Vault of Shia Islamic Books Glimpses of Shi'ism in the Musnad of Ibn Hanbal Chapter 4: the Prophet’s Declaration of Imam ‘ali-’s (‘a) Vicegerency Ahmad bin Hanbal says: Burayrah (Aslami-) has related: The Prophet (S) dispatched two regiments towards Yemen, one under the command of (Imam) ‘Ali- bin Abi- Ta-lib [(‘a)] and the other led by Kha-lid bin Wali-d with instructions that when the two regiments are with each other they should be under the sole command of (Imam) ‘Ali- [(‘a)], and when they are separate they will remain under different commanders.
We the Muslim forces, encountered the Yemeni tribe of Bani- Zayd and fought and defeated these infidels. When their men had died fighting, the families surrendered and from among the captives, (Imam) ‘Ali- [(‘a)] chose a maid for himself. Burayrah continues: Kha-lid bin Wali-d sent me to the Prophet with a letter informing him of this matter. I submitted the letter to the Prophet and when he had read it I saw signs of anger appear on his face.
I said: O Messenger of Allah (S), you sent me with a man instructing me to obey him, and accordingly I performed whatever duty I was ordered to do. The Messenger of Allah (S) said: La- taqa‘ fi- ‘Ali-yyin fa innahu minni- wa ana minhu wa huwa waliyyukum ba‘di- wa innahu minni- wa ana minhu wa huwa waliyyukum ba‘di- (Don't try to find faults with ‘Ali-, he is indeed from me and I am from him, he is your leader after me.