Twelve Caliphs (pbu th) [12 Shiites’ Imams] in Sunna’s Sources

Jabir 1said, “I was in.. presence of God’s messenger [prophet Muhamad (pbu h & h)] and I heard that he stated,”
“Due to existence of twelve caliphs, duty and condition of Ummah [people] are continuously obvious.”
Ahmad ibn Hanbal (of the Sunni elders) has written on page 86 of volume 5 of In his book “Musnad”:
“Jabir has narrated this narration via 34 ways.”
The narration has been seen in many other sources too, such as:

Musnad of Abu-Awanah, v.4, p.392
Al-Aynee, I. J. “Explanation of Bukhari”, v.24, p.281
Asghalanee, I. J. “Fath Al-Baree”, v.13, p.179
Al-Bidayah wa-nahayah, v.6, p.248
Al-Mo’jam Al-Kabir, p.94 & 97
Konooz Al-Hagha’eegh, p.208
Seyouti, I. J. “Tarikh Al-Kholafa’e”, p.61
Bukhari, I. J. “Al-Tarikh Al-Kabir”, v.2, p.158
Khateeb, I. J. “Tarikh Baghdad”, v.14, p.353
Hafiz, I. J. “Shawahid Al-Tanzeel”, v.1, p.455
Irshad Al-saree, v.10, p.328
Etc.

1-Jabir ibn ‘Abdullah ibn ‘Amr ibn Haram al-Ansari was a prominent companion of Muhammad.
From the article of Ayatollah Asefi, “Intizar Mo’ud” Journal, No.5