When someone is selling a vehicle, is the owner required to do a smog check prior to the sale?

My husband wants to sell a car and someone told him that according to California Law he is required to do a smog check before selling the car. Is this true or can he just make a deal with the person who he is selling to the car to, to lower the price so that the customer can do the smog check? My husband is just a regular guy selling a car, not a dealer or manufacturer.