"For upon you is a Prophet, a Siddiq, and two martyrs."(1)
This is a good and authentic hadith.

60 - Chapter
4031 - Abu Hisham al-Rifa'i narrated to us, saying: Yahya ibn al-Yaman narrated to us, from a Shaykh of Banu Zuhrah, from al-Harith ibn 'Abd al-Rahman ibn Abi Dhubab,
from Talhah ibn 'Ubayd Allah, who said: The Prophet, peace and blessings be upon him, said: "Every prophet has a companion, and my companion — meaning in Paradise — is 'Uthman."(2)
This hadith is ghareeb (unfamiliar), and its chain of transmission is not strong, and it is munqati' (disconnected).

61 - Chapter
4032 - 'Abd Allah ibn 'Abd al-Rahman narrated to us, saying: 'Abd Allah ibn Ja'far al-Raqqi informed us, saying: 'Ubayd Allah ibn 'Amr narrated to us, from Zayd — he is Ibn Abi Unaysah — from Abu Ishaq,
from Abu 'Abd al-Rahman al-Sulami, who said: When 'Uthman was besieged, he looked out over them--------------------------------------------
(1) An authentic hadith, recorded by al-Bukhari (3675) and (3699), Abu Dawud (4651), and al-Nasa'i in "al-Kubra" (8135). It is also in "al-Musnad" (12106).
(2) Its chain is weak due to its disconnection; al-Harith ibn 'Abd al-Rahman did not meet Talhah ibn 'Ubayd Allah, and due to the ambiguity of the Shaykh from Banu Zuhrah.
It was also recorded by Ahmad in "Fada'il al-Sahabah" 1/401 and 502 and 521, and Abu Ya'la (665).
It has a supporting witness from the hadith of Abu Hurayrah recorded by Ibn Majah (109), in which there is 'Uthman ibn Khalid, who is weak.