Devout (adjective) – earnest or sincere

Source: http://www.dictionary.com/browse/devout

I came across this word while reading “Cinderella” by Anne Sexton

“Once the wife of a rich man was on her deathbed and she said to her daughter Cinderella: Be devout. Be good.”

The word in this sentence is most likely the dying wife telling Cinderella to be sincere and to be a good person. This makes more sense because I did not understand what exactly the dying wife was trying to tell Cinderella other than to be good but I can see the similarity when she says be good and be sincere.