Musnad Ahmad 25:395

Abdullah said: I found in my father’s book, in his own handwriting: Mahdi ibn Ja’far al-Ramli narrated to us, al-Walid—meaning Ibn Muslim—narrated to us, from Ibn Jurayj, from ‘Ata’, from Ibn ‘Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Be lenient, and it will be shown leniency to you."