Musnad Ahmad 435:44

Yazid ibn Harun narrated to us, he said: Yahya ibn Sa'id narrated to us, that Sa'd ibn Ibrahim informed him, from al-Hakam ibn Mina, that Yazid ibn Jariyah al-Ansari informed him that he was sitting among a group of the Ansar, and Mu'awiyah came out to them and asked them about their conversation. They said: "We were in a conversation from the conversations of the Ansar." Mu'awiyah said: "Shall I not add to you a hadith I heard from the Messenger of Allah, may Allah bless him and grant him peace?" They said: "Yes, O Commander of the Faithful." He said: "I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: 'Whoever loves the Ansar, Allah the Almighty and Majestic loves him, and whoever hates the Ansar, Allah the Almighty and Majestic hates him.'"