Musnad Abu Ya'la al-Mawsili 115:368

Ahmad narrated to us, Hajjaj narrated to me, Shu'bah narrated to me, he said: I heard Qatadah narrating from Anas bin Malik that the Messenger of Allah (ﷺ) said: "The Ansar are my inner circle and my trusted confidants. Indeed, the people will increase while they will decrease, so accept from their doers of good and pardon their wrongdoers."