Stáli the Hewer believes you convinced Eskil Bloodthumb not to search Deepscrave for the jewels of the Steepset, and he hopes that you will do so on behalf of his assistant.
'Did you convince my apprentice not to enter Deepscrave? For shame, ${PLAYER}! You had no right to interfere in this matter.
'I will forgive you if you sign this contract agreeing to help me instead. The parchment is right here.'
Stáli the Hewer has presented you with a contract requiring you to assist him. It is your choice whether to sign the document or tell him no.
Durin asked you to examine the Berg-beam in Deepscrave for signs of weakness and to combat any Orcs you find there. While you are on the prince's business, you may as well keep your eyes open for the jewels sought by Stáli the Hewer.
Stáli the Hewer is waiting for you to emerge from Deepscrave and bring him the fruits of your search. He is at Maergrind in Máttugard.