Final answer:
Morris urges Mr. White to throw the paw into the fire to prevent the tragic consequences that come with the wishes it grants.
Step-by-step explanation:
Morris urges Mr. White to throw the monkey's paw into the fire because he is fully aware of the paw's dangerous magical abilities. He knows that while the paw can grant wishes, they come with a tremendous and often tragic price. Morris's own experiences and the dark, unsettling aura surrounding the paw compel him to advise Mr. White to destroy it, in hopes to prevent further misery and potential disaster.