Musnad Ahmad 32:1605

Surayj narrated to us, Suhayl, the brother of Hazm ibn Abi Hazm al-Qut'i, narrated to us, he said: Thabit al-Bunani narrated to me, he said: I heard Anas ibn Malik saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, recite this verse: {And you do not will except that Allah wills} {He is worthy of fear and worthy of forgiveness} [Al-Muddaththir: 56]. Then the Messenger of Allah, peace and blessings of Allah be upon him, said: "Your Lord says: 'I am worthy that I should be feared, that another god be set up with Me. And whoever fears that another god be set up with Me, then he is worthy that I should forgive him.'"