Sunnah prayers have many benefits, some of which may be outlined as follows:
1- Sunnah or Voluntary Prayers bring more reward to Allah’s servant, as increasing voluntary Prayers is the best of supererogatory acts after Jihad in the Cause of Allah.
2- Sunnah Prayers compensate and make up for any shortcoming or incompleteness in the obligatory Prayers.
3- The Prophet (peace and blessings be upon him) is reported to have said: Whoever prays twelve unit Rak`at during the day and night will have a house built for him in Paradise.” (At-Tirmidhi)
4- It is stated in a hadith that whenever a Muslim prostrates to Allah, He will elevate him one degree and forgive him one bad deed.” (At-Tirmidhi)
5- Sunnah Prayers increase the light of Iman (faith) in the heart, as each Prayer brings light to the heart of Muslim.
Supererogatory prayers include, but not limited to; some unit Rak’at before and after some obligatory prayers, Tahiyyatul Masjid, Night prayer (Tahajjud), Saltud Duha, Salatu Tasbih, Salat al-Khwf etc.
Explaining these prayers in details requires extensive, and even voluminous study.