Narrated 'Abdul-Muttalib bin Rabi'ah bin Al-Harith bin 'Abdul-Muttalib:
"Al-'Abbas bin 'Abdul-Muttalib entered upon the Messenger of Allah (ﷺ) in a state of anger while I was with him, so he said: 'What has angered you?' He said: 'O Messenger of Allah, what is it with us and the Quraish, whenever they meet one another it is with glad faces, and when they meet us they meet us with other than that?'" He said: "So the Messenger of Allah (ﷺ) became angry, until his face reddened, then he said: 'By the One in Whose Hand is my soul! Faith does not enter a man's heart until he loves you for the sake of Allah, and for the sake of His Messenger.' Then he said: 'O people! Whoever harms my uncle, he has harmed me, for indeed, a man's uncle is not but the Sinw (two or three palm trees will come from a single root, so each is called a Sinw. A man's uncle is like that to his father. That is, he is like his father) of his father."
English reference: Vol. 1, Book 46, Hadith 3758
Arabic reference: Book 49, Hadith 4125