Ali bin Abu Talib reported,
"Abu Juhayfah, shall I tell you who is the best of this ummah after its Prophet?"I said, "Yes," though I did not think there was anyone better than him.He said, "The best of this ummah after its Prophet is Abu Bakr, and after Abu Bakr is Umar 
, and after them there is a third," but he did not name him.
Ahmad 835
Sahihحدثنا إسماعيل بن إبراهيم أنبأنا منصور بن عبد الرحمن يعني الغداني الأشل عن الشعبي حدثني أبو جحيفة الذي كان علي يسميه وهب الخير قال
قال علي رضي الله عنه
يا أبا جحيفة ألا أخبرك بأفضل هذه الأمة بعد نبيها قال قلت بلى قال ولم أكن أرى أن أحدا أفضل منه قال أفضل هذه الأمة بعد نبيها أبو بكر وبعد أبي بكر عمر رضي الله عنه وبعدهما آخر ثالث ولم يسمه
Its isnad is sahih. Al-Ashall is trustworthy, Ahmad, Ibn Main, and Abu Dawud affirmed his reliability, and Bukhari mentioned him in al-Kabir 4/1/345-346 without noting any criticism of him. Al-Ghudani is with a damma on the ghayn and a light dal, a relation to Ghudanah bin Yarbu bin Hanzala, a clan of Tamim. See al-Mushtabih by Dhahabi, pages 354 and 384, and al-Ansab, folio 406.Wahb al-Khayr, it is established by this isnad that it was Ali who named him this, yet the Hafiz related this in al-Tahdhib using the weak formula "it is said," which is not good. He alluded to this isnad in al-Fath 6:27. The hadith carries the same meaning as the one before it.