Jami` at-Tirmidhi 3362

Ibn Abbas said:“Umar used to ask me questions in front of the Companions of the Prophet. So Abdur-Rahman bin Awf said to him: ‘Why do you ask him, while we have children like him?’” He said: “Umar said to him: ‘It is because of what you know (about him).’ So he asked him about this Ayah: ‘When there comes the help of Allah and the Conquest.’ I said: “It is only regarding the (end of the) life span of the Messenger of Allah, informing him of it.” Then he recited the Surat until its end. So Umar said to him: “By Allah! I know not about it, but what you know.”