From Sahih Muslim (Hadith 1696):
Umm Habiba, the wife of the Messenger of Allah (ﷺ), reported Allah's Messenger (ﷺ) as saying: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)
Reference: Muslim 1696