Ibn Abbas was a young man in his mid-20s when Umar passed away. He narrates this story just when permission had come from Aisha allowed Umar to be buried in the same room next to the Prophet ﷺ and Abu Bakr.
Ibn Abbas narrates:
On the day that Umar was stabbed and killed, I was standing there when Umar was placed on his bed as he was dying. As I was standing there I felt on my shoulder somebody’s elbow leaning over me. I heard him say: “May Allah have mercy on you, I always hoped that Allah would place you together with your two companions, because how often did I used to hear the Prophet ﷺ say ‘I used to… along with Abu Bakr and Umar’ and ‘I did… with Abu Bakr and Umar’ and ‘I went… along with Abu Bakr and Umar’, and so I wanted you to be with them in death as well.” I looked back to see who was the person speaking, and it was Ali ibn Abu Talib.
Source: Sahih Bukhari, narrated by Yasir Qadhi, Lives of the Sahaba, Abu Bakr, Part 3