`` Homer vs. Lisa and the 8th Commandment '' is the thirteenth episode of the second season of The Simpsons , which first started on February 7 , 1991 . `` Homer vs. Lisa and the 8th Commandment '' is the thirteenth episode of The Simpsons second season and the 26th episode overall . It originally aired on the Fox network in the United States on February 7 , 1991 .