Umar (May Allah be pleased with him) used to make me sit with the noble elderly men who had participated in the battle of Badr. Some of them disliked it and said to 'Umar: "Why do you bring in this boy to sit with us when we have sons like him?" 'Umar replied: "Because of the status he has, which you already know about (i.e., belongs to the source of knowledge and the house of the Prophet (ﷺ))." One day, 'Umar called me and seated me in the gathering of those people; and I think that he called me just to show them (of my religious knowledge). 'Umar then questioned them (in my presence). "How do you interpret the ayah of Allah: 'When there comes the Help of Allah (to you, O Muhammad (ﷺ) against your enemies) and the Conquest (of Makkah)."' Someone said that when Allah's Help and the Conquest (of Makkah) came to us, we were called upon to celebrate the Praise of Allah and ask for His forgiveness. Some others remained silent and did not utter a word. Thereupon 'Umar asked me: "Ibn 'Abbas! Do you say the same." I replied: "No". He said: "What do you say then?" I replied: "That is the sign of the Prophet's death about which he had been informed. Allah, the Exalted, says:

'When there comes the help of Allah (to you, O Muhammad (ﷺ) against your enemies) and the Conquest (of Makkah)'.

So declare the remoteness of your Rubb from every imperfection, and ask for His forgiveness. Verily, He is the One Who accepts the repentance and Who forgives".

On that 'Umar (May Allah be pleased with him) said: "I do not know anything about it other than what you have said".

[Al- Bukhari]