What is meant by the prayer that restrains its practitioner from indecency and wrongdoing?

Question : If someone were to say, "We pray five times a day and perform voluntary prayers as Allah wills, yet we find nothing in our hearts that restrains us from indecency and wrongdoing," what is the answer?

Answer : And Allah says: This is a confirmed report. The answer is that the prayer referred to is the complete prayer that encompasses what Allah and His Messenger have commanded.
And it involves staying away from what Allah and His Messenger have forbidden. The most important aspect is khushu' (humility), which is the presence of the heart; this is the essence and spirit of the prayer. If a person is humble and his heart is present, he feels a distinct sensation when he finishes the prayer that his heart has been refreshed and has changed from its previous state. As for entering the prayer while asking Allah to treat us with His pardon, and the person starts the prayer while his intrusive thoughts are open to him, then when he tries to block them—meaning, when he tries to block them—his heart is filled with things as if stones are thrown into the sea; he is filled with something he was not thinking about at all, then he blocks it, then another comes, then he blocks it, then another comes. Therefore, I call myself and you to khushu' (humility) and the presence of the heart, for that will help you with the results that occur in the prayer. Indeed, it will realize for you the good results and the great fruits that come from the prayer.