´Narrated Al-Bara:` "The Prophet (ﷺ) dispatched two armies and put 'Ali bin Abi Talib in charge of one of them, and Khalid bin Al-Walid in charge of the other. He said: "When there is fighting, then (the leader is) 'Ali." He said: "So 'Ali conquered a fortress and took a slave girl. So Khalid sent me with a letter to the Prophet (ﷺ) complaining about him. So I came to the Prophet (ﷺ) and he read the letter and his color changed, then he said: 'What is your view concerning one who loves Allah and His Messenger, and Allah and His Messenger love him.'" He said: "I said: 'I seek refuge in Allah from the wrath of Allah and the anger of His Messenger, and I am but a Messenger.' So he became silent."
Hadith Referenceسنن ترمذي / كتاب المناقب عن رسول الله صلى الله عليه وسلم / 3725
Bara’ (may Allah be pleased with him) says that the Prophet (peace and blessings of Allah be upon him) sent out two armies: he appointed Ali ibn Abi Talib (may Allah be pleased with him) as the commander of one, and Khalid ibn Walid (may Allah be pleased with him) as the commander of the other, and said: “When there is fighting, Ali will be the commander.” Ali (may Allah be pleased with him) conquered a fortress and took a slave woman from it. Khalid ibn Walid (may Allah be pleased with him) sent me with a letter to the Prophet (peace and blessings of Allah be upon him). I came to the Prophet (peace and blessings of Allah be upon him), and when he read the letter, his face changed color. Then he said: “What do you think about a man who loves Allah and His Messenger, and Allah and His Messenger love him?” I said: I seek refuge with Allah from the anger of Allah and His Messenger; I am only a messenger. So he remained silent.
Explanation: 1: Both these armies were dispatched towards Yemen.
2: That is, if upon arrival, combat with the enemy begins immediately, then Ali radi Allahu anhu will be the commander; and if both armies remain separate, then Ali radi Allahu anhu will be the commander of one and Khalid radi Allahu anhu of the other.
3: That is, the Messenger of Allah sallallahu alayhi wa sallam sent me under the authority of another man; I accepted his authority, obeyed him, and brought this letter written by his hand to your (sallallahu alayhi wa sallam) presence. So what fault is mine in this? Upon hearing this, you (sallallahu alayhi wa sallam) remained silent.
Note: (Its narrator Abu Ishaq is a mudallis and has mixed narrations, but through the narration of Imran bin Husayn (with the author under number 3712), this hadith is authentic.)
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 1704