This is an excerp from the work of imam birkiwi ra on the way grave worsgip entered islaam and how it developed and also the verdict concerning asking the grave dwellers for help!!.

He mentions-:

“if you are in doubt about this issue then let us see if any person on the face of the earth ia capable of bringing forward any proof that is saheeh or hasan or even daeef or even munqati3 ( in other words proove asking from the dweelers being permiisible from even a weak narration ) .

The grave worshippers habit is that at time of need they  visit the graves and  make du’aa there and touch the grave.  In addition they would pray to the grave and ask from Allah using the Grave dweller’s waseela and further ask directly from the occupants their needs.
The onus is upon them to bring forward even one narration to proove this. Never ever!! they will never be able to do so.
Rather they will be able to bring forward many narration from the khalf(those who were not from the khairul quroon) who came afterwards and as time passed this increased to such an extent that many books were authored
that had no narration from Rasululaah saaws nor from the khulafa Raashideen nor from the Sahaabah and the Taabi een even one letter in favour of their actions, rather there are many narrations opposing it.

In a  marfoo3 hadeeth it is  narrated that rasululaah saawx ordered, ‘i prevented you previously from visiting the grave so whoever visits the grave or intends to visit the grave should do so and should refrain form saying words of open sin’
(the author says) Which sin is greater than commiting shirk at the grave either by statement or action.