@Imam Ali: He was a Tabi'ee.
@scusemyenglish: Interesting point.
Yes the fist time I have heard this hadith is one Ahlou Lbidar he says " Look Kaab want to introduce jew habit into islam because he wants to pray behind the rock..."
I think it's his Ijtihad. he was thinking that is better. But Omar says the contrary. The most important for me it's
Kaab has contributed to build masjid Al Aqsa irrepective his personal ijtihad! He was "just" a tabi'i it's normal if he has a point a view different of Omar....
The Most important thing. Kaab Has contributed to build a masjid on the most holy place for judaism! It is the proof he loves Islam than more all. And he has the confidence of Omar!
I intend to talk about that point in my refutation on Abou Hourayra. For show Kaab is a man reliable. Contrary I will show the real jewish influence on shia creed.
For example in jew people there is "Marranism" of espagna. they show they are christian to all appearance but truly they are jew.
It's like Taquiya .then Some jews curse Maryam and some Shia curse mother of believers. etc etc etc etc etc...
That is real common trait between shia and some jew. It's not a joke like kaab el Ahbar and the error with the hadith on the creation in 6 or 7 days withtch change nothing.
If Kaab was a spy, For example he would say "Aisha has killed the messenger! puh" for washing jew people.
this is what he would have said!
it should be noted that many jew orientalist like Goldziher want to contest the status of Qods into Islam... And all his studies are present in Israel today...