Hadith No: 1
Ibn Abi Asim - al-Ahad wa al-Mathani - al-‘Asharah al-Mubashshirun bil-Jannah
And among those who mentioned Ali ibn Abi Talib, son of Abd al-Muttalib, son of Hashim, son of Abd Manaf ...
Volume: (1) - Page Number: (148)
178 - Abu Bakr narrated to us: Ibn Numayr narrated to us, from al-Ala ibn Saleh, from al-Minhhal ibn Amr from Ubad ibn Abd Allah, who said: I heard Ali (may peace be upon him and his holy progeny) say: "I am the servant of Allah and the brother of His Messenger," and "I am the greatest truthful one (al-Siddiq al-Akbar); none will say it after me except a lying, fabricating person. And I prayed before the people for seven years."

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Reference: Al-Aahaad wa al-Mathaani Book 1

Hadith No: 2
Ibn Abi Asim - Kitab al-Sunnah - Chapter on What is Mentioned about the Virtue of Ali (ra)
Volume: (2) - Page Number: (598)
1324 - Narrated to us by Abu Bakr ibn Abi Shaybah, who said: Abdullah ibn Numayr narrated to us, from al-Ala ibn Salih, from al-Munhal from Ubad ibn Abdullah, who said: I heard Ali (peace be upon him) say: "I am the servant of Allah and the brother of His Messenger," and "I am the greatest truthful one (al-Siddiq al-Akbar). No one will say this after me except a lying fabricator." And I prayed before the people seven years.

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Reference: Kitaab al-Sunnah Book 2