If the above Sunni account were true...
If the above Sunni account were true, it would imply that Umar's assassination was a conspiracy of Ka'b and his associates. Announcing the event before it took place would make the companions believe in what Ka'b predicted and what he claimed to be recorded in the Old Testament, therefore making him a reliable source for future information. Such confidence would enable him to interfere in major events and suggest the name of the future Caliph.
A number of prominent companions believed the information that Ka'b used to fabricate pertaining to the past and the future. On the other hand, if the above prediction of event, documented in the Sunni history, is false and a pure fabrication, then it shows how much Ka'b and his supporters among the Sunnis were able to fabricate historical documents to elevate Ka'b's position, and to manipulate the history of Islam.
Kaab did not speak only about the events that happened on the earth, but he also gave information concerning the heavens and the Divine throne. Al Qurtubi in his Commentary on the Quranic Chapter of Ghafir reported that Kaab said : When God created his throne, the throne said : ' God didn't create any creature greater than me. ' The throne then shook itself to show it's glory.
God roped the throne with a snake which had 70 thousand wings; each wing had 70 thousand feathers; each feather had 70 thousand faces; each face had 70 thousand mouths, and each mouth had 70 thousand tounges. Out of these mouths words glorifying Allah with a quantity equal to the number of drops of rain that have fallen, and the leaves on the trees, and the number of pieces of gravel and soil and the number of the days of the world, and the number of angels.
The snake coiled around the throne, for the throne was much smaller than the snake. The throne was covered by only half the snake. Imam Ali's ( as ) attitude towards Kaab Umar and a number of prominent companions had a very positive attitude towards Kaab. However the most knowledgable and the most farsighted among them, namely, Imam Ali ( as ) discredited Kaab. Kaab did not dare to come close to Imam Ali ( as ), despite the fact that the Imam was in Medina for the duration of Kaab's stay.
It is reported that Imam Ali ( as ) said about Kaab : Certainly he is a professional liar !