question #1 Sahih Muslim 728c, Book 6, Hadith 126 : What is the significance of performing additional voluntary prayers in Islam?

If any Muslim servant (of Allah) prays for the sake of Allah twelve rak’ahs (of Sunan) every day, over and above the obligatory ones, Allah will build for him a house in Paradise, or a house will be built for him in Paradise; and I have not abandoned observing them after (hearing it from the Messenger of Allah). (So said also ‘Amr and Nu’man.)