Excellence of the Twelve Units of Voluntary Prayers

Umm Habibah (May Allah be pleased with her) the Mother of the Believers reported: I heard the Messenger of Allah (sallallaahu ’alayhi wa sallam) saying, “A house will be built in Jannah for every Muslim who offers twelve Rak`ah of optional Salat other than the obligatory Salat in a day and a night (to seek the Pleasure of Allah).”
[Muslim].

Commentary: Tatawwu` means to offer more Nawafil (optional prayers) on one’s own after performing the Faraid (obligatory prayers). Thus, this Hadith tells us the merits of optional prayers and holds promise of (Jannah) for those who make it a practice.

Further Reading :

• Advice to Those Who Are Not Praying Any Nawaafil Prayers – Shaykh Muhammad ‘Umar Baazmool
• The Excellence of Optional Prayers (Sunnah Mu’akkadah) along with the Obligatory Prayers – Riyadh ul Saleheen
  
• Al-Sunan al-Rawatib (Sunnah Mu’akkadah) – Shaik ibn Baaz -Taken from the Book :: Prophet Muhammad’s Manners of Performing Prayers