Immodest plays and dances are forbidden by the sixth Commandment, and it is sinful to look at them. Immodest plays and dances. Any amusements by which we may commit sins against holy purity. • Does the sixth Commandment forbid immodest songs, books, and pictures? The sixth Commandment forbids immodest songs, books, and pictures, because they are most dangerous to the soul, and lead to mortal sin. Immodest books. Books which may lead us to commit sin either in thought, word or deed. The Commandment is broken by sins against the virtue of Purity.