Musnad Ahmad 25:1131

Wahb ibn Jarir narrated to me, my father narrated to us, he said: I heard Yunus narrating from al-Zuhri, from Ubayd Allah ibn Abd Allah, from Ibn Abbas, who said: When the death of the Messenger of Allah (peace and blessings of Allah be upon him) approached, he said: "Come, I will write for you a document, after which you will never go astray." There were men in the house, among them Umar ibn al-Khattab. Umar said: "The Messenger of Allah (peace and blessings of Allah be upon him) is overcome by pain, and you have the Quran; the Book of Allah is sufficient for us." The people in the house differed and disputed. Some of them said: "Let the Messenger of Allah (peace and blessings of Allah be upon him) write for you," or he said: "Bring [writing materials] so the Messenger of Allah (peace and blessings of Allah be upon him) may write for you." Others said what Umar had said. When they increased the clamor and the disagreement, and it distressed the Messenger of Allah (peace and blessings of Allah be upon him), he said: "Get up and leave me." Ibn Abbas used to say: "The calamity, the entire calamity, is what came between the Messenger of Allah (peace and blessings of Allah be upon him) and his writing that document for them, due to their disagreement and their clamor."