From the Prophet ﷺ: “Ṭalḥah and al-Zubayr are my neighbors in Paradise (1).”

Abu Jaʿfar al-Razi reports—through Ḥuṣayn, from ʿAmr ibn Maymūn—who said:
ʿUmar declared, “People are saying: ‘Appoint a successor over us.’ If something should happen to me, then the matter is to be decided by these six with whom the Messenger of Allah ﷺ parted while pleased with them.” He then named them.

Ahmad, in his Musnad, relates: Zakariyyā ibn ʿAdī narrated to us; ʿAlī ibn Mushir narrated to us, from Hishām, from his father, from Marwān—whom I do not think suspect—who said:
“ʿUthmān was struck by a severe nose-bleed in the Year of the Nose-bleed, to the point that he stayed behind from the pilgrimage and wrote his will. A man from Quraysh came in to him and said, ‘Appoint a successor.’
‘Have they said that?’ ʿUthmān asked.
‘Yes,’ he replied.
‘Who is it?’ ʿUthmān asked, but the man fell silent.
Then another man entered and said the same, and ʿUthmān answered him in the same way.
Finally ʿUthmān said, ‘Are they suggesting al-Zubayr?’
They said, ‘Yes.’
He said, ‘By Him in whose hand is my soul, to the best of my knowledge he is indeed the finest of them (2) and the most beloved of them to the Messenger of Allah (3) ﷺ.’”

It was also transmitted by Abū Marwān al-Ghassānī (4) from Hishām with similar wording.

Hishām further reported, on the authority of his father, that ʿUmar said: “Had I nominated anyone or left a testament, he would have been the dearest of them to me…”