Musnad Ahmad 384:1

Abdullah ibn Ahmad said: Yahya ibn Ma'in narrated to me, he said: Abu Ubaydah—meaning al-Haddad—narrated to us, he said: Abd al-Aziz ibn Muslim narrated to us, from Yazid ibn Abi Mansur, from Dhu al-Lihyah al-Kilabi, that he said: "O Messenger of Allah, do we act in a matter that is newly begun, or a matter that has already been finished?" He said: "No, rather in a matter that has already been finished." He said: "Then why do we act?" He said: "Act, for everyone is facilitated for that which he was created for."