Cats scratch as a way of marking territory, so anything sprayed on the furniture that removes its scent can help. Effective pet odor removal sprays utilize biological enzymes that break down the residue of the cat odor to create a neutral smelling site.
Sprays infused with orange could convince him to avoid that spot. Other citrus fruit scents will also work to help dissuade the cat from scratching the furniture, such as lemon. A strong, bitter apple spray is also unappealing to cats.
Herb-based spray products are available to make the furniture smell repulsive to cats. These sprays are sold by pet supply stores and through veterinarian's offices that carry pet supplies.
This spray needs to go on something you want the cat to scratch. Place the post within the cat's sight line of the furniture you want him to stop scratching. Pick up the cat and take him to the sprayed item whenever he approaches the furniture. Cats International suggests rubbing catnip into the post itself.