Musnad Ahmad 28:563

Hassan ibn Musa al-Ashyab narrated to us, Hariz—meaning Ibn Uthman al-Rahbi—narrated to us, from Habban ibn Zayd, from Abdullah ibn Amr ibn al-As, that he heard the Prophet, peace and blessings of Allah be upon him, saying upon his pulpit: "Show mercy, and you will be shown mercy; and forgive, and Allah will forgive you. Woe to the funnels of speech. Woe to those who persist, who persist in what they have done while they know."