Answered by: Maulana Mujahid Hussain
Please source the original Hadith book this scholar is quoting, and authenticate.
A man from the Khawarij came to Ameer ‘Ali (ra) and said to him: “What is wrong with you, that the people disagreed on you and ‘Uthman, while they agreed on Abu Bakr and ‘Umar?” so ‘Ali answered: “The people agreed on Abu Bakr and ‘Umar when the people were me and ‘Uthman, and they disagreed on me and ‘Uthman when they were like you and your likes [Miraat al-Jinan_ 1/95 مرآةالجنانوعبرةاليقظان
By Abi Muhammad Abdullah bin As-aad al-Yaafi al-Yamani al-Makki]
بسم الله الرحمن الرحي
Unfortunately, I could not find it in any books written by the Salaf Saleheen with a chain of narration. As I result I cannot help you in this regard.
It is mentioned by latter scholars such as Ibn Imaad Hanbali in شذرات الذهب في أخبار من ذهب page 226 volume 1 Dar Ibn khathir print, but without a reference dating back to the time of Ali ( رضي الله عنه )
I encourage you to ask other scholars also. If you manage to find the original source then please share it with us . Jazakallah Kharan
Only Allah Knows best.
Written by Maulana Mujahid Hussain
Checked and approved by Mufti Mohammed Tosir Miah
Darul Hadith Birmingham