صلاة النافلة
Ṣalāh al-Nāfila
A voluntary ritual prayer offered in addition to the obligatory ones; it earns reward when performed and carries no blame when omitted.
What it means
Nāfila means an addition or a surplus, and ṣalāh al-nāfila is the optional prayer that a Muslim adds to the obligatory ones. The best known is the night vigil, tahajjud. The Quran tells the Prophet to rise at night for it as an additional duty for him (17:79). Voluntary prayers are offered at many times: before or after the obligatory prayers, in the forenoon (ḍuḥā), and on greeting a mosque. Their purpose is to bring the worshipper nearer to God and to make up any shortfall in the obligatory prayers. Performing them is commendable, and leaving them out brings no sin.
Often misunderstood as
Calling these prayers optional can suggest that they matter little, although the tradition treats them as a major means of growing close to God.
What the sources say
A hadith qudsi in Sahih al-Bukhari reports God saying that His servant keeps drawing near to Him through voluntary acts of worship until He loves him. The Prophet Muhammad (peace be upon him) also said that the best prayer after the obligatory prayers is the prayer in the middle of the night (Sahih Muslim).
Term and Arabic as listed in Ismail al Faruqi, Toward Islamic English (International Institute of Islamic Thought, 1995), p. 55, listed as SALAH AL NĀFILAH. The definition is restated here.