from the Prophet (ﷺ): "For whomever I am his Mawla then 'Ali is his Mawla."
Jami` at-Tirmidhi Book 49, Hadith 109
← Previous Hadith that the Messenger of Allah (ﷺ) dispatched an army and he put 'Ali bin Abi Talib in charge of it. He left on the expedition and he entered upon a female slave. So four of the Companions of the Messenger of Allah (ﷺ) scolded him, and they made a pact saying: " we meet the Messenger of Allah (ﷺ) we will inform him of what 'Ali did." When the Muslims returned from the journey, they would begin with the Messenger of Allah (ﷺ) and give him Salam, then they would go to their homes. So when the expedition arrived, they gave Salam to the Prophet (ﷺ), and one of the four stood saying: "O Messenger of Allah! Do you see that 'Ali bin Abi Talib did such and such." The Messenger of Allah (ﷺ) turned away from him. Then the second one stood and said as he said, and he turned away from him. Then the third stood before him, and said as he said, and he turned away from him. Then the fourth stood and said as they had said. The Messenger of Allah (ﷺ) faced him, and the anger was visible on his face, he said: "What do you want from 'Ali?! What do you want from 'Ali?! What do you want from 'Ali?! Indeed 'Ali is from me, and I am from him, and he is the ally of every believer after me."

Jami` at-Tirmidhi Book 49, Hadith 108 Next Hadith → that the Messenger of Allah (ﷺ) said: "May Allah have mercy upon Abu Bakr, he married me to his daughter, and he carried me to the land of Hijrah, and he freed Bilal with his wealth. May Allah have mercy upon 'Umar, he says the truth even if it is sour. The truth caused him to be left without a friend. May Allah have mercy upon 'Uthman, the angels are shy of him. May Allah have mercy upon 'Ali. O Allah! Place the truth with him wherever he turns."

Jami` at-Tirmidhi Book 49, Hadith 110