Besides the mandatory (Farj) prayers, our beloved Prophet (Pbuh) used to say voluntary (Nafl) prayers too. It is mentioned in the hadith that the voluntary prayer is a means of attaining closeness to Allah.
Through voluntary prayers, a person receives additional rewards and through these prayers (s)he gets closer to Allah. A person will be asked about his obligatory prayers first on the Day of Judgment, if it is imperfect, then optional prayers will perfect it. Narrated Abu Hurayra (Ra.) that, our beloved prophet said: “Indeed the first deed by which a servant will be called to account on the Day of Resurrection is his Salat. If it is complete, he is successful and saved, but if it is defective, he has failed and lost. So if something is deficient in his obligatory (prayers) then Allah will say: ‘Look! Are there any voluntary (prayers) for my worshipper?’ So with them, what was deficient in his obligatory (prayers) will be completed. Then the rest of his deeds will be treated like that.” (Tirmiji).The most beneficial voluntary prayer is Tahajjud. The word Tahajjud means ‘awake at night’. The prayer which is performed during the period from midnight up to the appearance of the early dawn called Tahajjud. Even though Tahajjud is not an obligatory prayer but after obligatory (Farj) prayer it is regarded with the highest standard. Abu Huraira (Ra.) reported that the Messenger of Allah (Pbuh) was asked as to which prayer was the most excellent after the obligatory prayers. He said, ‘Prayer offered in the depth of the night’. (Sahih Mulim). Allah says about the superiority of Tahajjud prayers: “And some part of the night awake for its recital, as voluntary worship for you. It may be that your Lord will raise you to a praised estate.” (Sura Al-Isra: Ayat 79).According to the hadith, the night prayer (Tahajjud) is most rewarding prayer after the obligatory prayers. The performer of Tahajjud will enter paradise safely. Abd Allah ibn Salam (Ra.) reported that the Messenger of Allah (Pbuh) said, “O people! Spread the salams (salutations), feed the people, maintain the ties of kinship, and pray at night when others sleep and you will enter paradise in peace (safely).” (Tirmidhi).The minimum limit for Tahajjud prayer is 2 rakats. It has no maximum limit. Optimal limit for this prayer is 8 rakats, because this was the general practice of the Messenger of Allah (Pbuh). Recitation from the holy Qur’an for long in Tahajjud prayer is also recommended. The night prayer (Tahajjud) may be performed also in the early part of the night (after the obligatory Isha prayer), the middle part of the night, or the ending part of the night, but it is the best to wake up in the middle of the night for performing the Tahajjud prayer. If one is not sure about whether he will be able to wake up, then (s)he can pray 4 rakats right after the 2 rakats of Sunnat-e-mu’akkadah of Isha prayer with the niyyat (intention) of Tahajjud. Although, the reward, in this case, will be much less, many religious experts have advised this method for those who find it difficult to wake up later in the night.Another beneficial voluntary prayer is Awabeen. Awabeen are the plural of Arabic word ‘Awab’ and this refers to one who is obedient, or turns to obedience, or who submits himself to the worship of Allah by asking for forgiveness. After performing the Farj and sunnah of Maghrib prayer, one may perform 6 rakats of Awabeen prayer. One who prays Awabben, he will get the best reward. Abu Hurairah (Ra.) narrated that Allah’s Messenger (Pbuh) said: “Whoever prays six rakats after Maghrib prayer, and he does not speak about anything between them, it would be equivalent to twelve years of worship for him.” (Jame Tirmiji).We should make a habit of praying Tahajjud and Awabeen prayers so that we can be benefited throughout our worldly and spiritual life.