Sahih al-Bukhari Book 62, Hadith 36
The Prophet (ﷺ) ascended the mountain of Uhud and he was accompanied by Abu Bakr, `Umar and
`Uthman. The mountain shook beneath them. The Prophet (ﷺ) hit it with his foot and said, "O Uhud ! Be
firm, for on you there is none but a Prophet, a Siddiq and a martyr (i.e. and two martyrs).
When (the dead body of) `Umar was put on his deathbed, the people gathered around him and invoked (Allah) and prayed for him before the body was taken away, and I was amongst them. Suddenly I felt somebody taking hold of my shoulder and found out that he was `Ali bin Abi Talib. `Ali invoked Allah's Mercy for `Umar and said, "O `Umar! You have not left behind you a person whose deeds I like to imitate and meet Allah with more than I like your deeds. By Allah! I always thought that Allah would keep you with your two companions, for very often I used to hear the Prophet (ﷺ) saying, 'I, Abu Bakr and `Umar went (somewhere); I, Abu Bakr and `Umar entered (somewhere); and I, Abu Bakr and `Umar went out."'
Ibn `Umar asked me about some matters concerning `Umar. He said, "Since Allah's Messenger (ﷺ) died. I have never seen anybody more serious, hard working and generous than `Umar bin Al-Khattab (till the end of his life."