Umm Habiybah (May Allah be pleased with her) the Mother of the Believers reported: I heard the Messenger of Allah (Peace be upon Him) saying,

"A house will be built in Jannah for every Muslim who offers twelve Rak’ah of optional Salaah other than the obligatory Salaah 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 Faraidh (obligatory prayers). Thus, this Hadith tells us the merits of optional prayers and holds promise of (Jannah) for those who make it a practice.

These Nawaafil are as follows

2 Rakaah before Fajr

4 Rakaah  ( prayed in twos or four together) before Dhuhr*

2 Rakaah after Dhuhr

2 Rakaah after Maghrib

2 Rakaah after Isha

There is another naration from the Messenger of Allah ( peace be upon him) according to Bukhari and Muslim saying these are 10 rakaah ( with the exception of Dhuhr where only 2 Rakaah before Dhuhr are performed.

*The 2 or 4 Rakaah before Dhuhr can be performed together praying all four  with one Tashahhud at the end. Or they can be performed  with 2 Tashahhud which is the best. They can be performed as 2 rakaah only following another hadith of the Messenger of Allaah. All these are acceptable due to having authentic source from the Messenger of Allah.