Musnad Ahmad 33:485

Harun ibn Ma'ruf narrated to us, Ibn Wahb narrated to us, 'Amr informed me, from Abu al-Zubayr, from Jabir, that he said: "O Messenger of Allah, do we act for a matter that has already been finished, or for a matter that we are just beginning?" He said: "For a matter that has already been finished." Suraqah said: "Then why act, if so?" The Messenger of Allah, may Allah bless him and grant him peace, said: "Every worker is facilitated for his work."