Imam Al-Nawawi's Riyad-us-Saliheen
Chapter 198
Desirability of Lying down on one's right side after the Sunnah of Fajr Prayer

1110.`Aishah (May Allah be pleased with her) reported: When the Prophet (sallallaahu ’alayhi wa sallam) had performed two Rak`ah before the Fajr prayer, he would lie down on his right side.
[Al-Bukhari].

1111. `Aishah (May Allah be pleased with her) reported: When the Prophet (sallallaahu ’alayhi wa sallam) finished the `Isha prayer, he would perform eleven Rak`ah before the Fajr prayer, concluding each two Rak`ah with Taslim (i.e., saying As-Salamu `Alaikum) and observing the Witr (odd) at the end. When the Mu'adhdhin finished proclaiming Adhan for the Fajr prayer and it was dawn, he would rise and perform two short Rak`ah, and then would lie down on his right side till the Mu'adhdhin came to (inform) him about Iqamah.
[Muslim].

Commentary: This Hadith tells us that the Prophet (sallallaahu ’alayhi wa sallam) was in the habit of lying down on his right side after the two Sunnah of Fajr prayer. It also mentions his offering of Tahajjud prayer, which consists of eleven Rak`ah. He would perform this Salat in the form of four couplets and one Witr. According to some narrations, he would perform four couplets and supplement them with three Rak`ah of Witr. Both these forms are right. This Hadith, also proves the validity of one Witr.

This Hadith also tells us that the time for the Tahajjud and Witr prayer is from `Isha' prayer to the daybreak. One can perform Tahajjud prayer at any time during this period. But, the best time for it is the third part of the night for the reason that after Tahajjud one can, after a while, perform Fajr prayer in congregation (Jama`ah).

The Tarawih (optional night prayer) performed in the month of Ramadan is this Tahajjud prayer which is also termed as Qiyam-ul-Lail For the sake of convenience and benefit of congregational prayer, it is offered soon after `Isha' prayer in the month of Ramadan. The right number of Rak`ah in the Tarawih prayer is eight because the Prophet (sallallaahu ’alayhi wa sallam) never offered more than eight Rak`ah; with three Witr in the month of Ramadan or otherwise. `Aishah's statement to this effect quoted in Sahih Al-Bukhari also supports this fact. In Hadith literature, the Nawafil of the night have been termed as Qiyam-ul-Lail for which the word "Tahajjud'' has also been used in the Qur'an and Hadith. The word "Tarawih'' does not figure anywhere in Hadith. The word "Tarawih'' for "Qiyam-ul-Lail'' became popular after the era of the Prophet (sallallaahu ’alayhi wa sallam) and his Companions. Thus, that number of Tarawih prayer agrees with the Sunnah of the Prophet (sallallaahu ’alayhi wa sallam) which is proved by the actual practice of the Prophet (sallallaahu ’alayhi wa sallam), that is eight Rak`ah and three Witr only. It is not in any case twenty Rak`ah. Authentic Ahadith prove this point abundantly.

1112. Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (sallallaahu ’alayhi wa sallam) said, "When anyone of you has performed two of Sunnah before the Fajr prayer, he should lie down on his right side."
[Abu Dawud and At-Tirmidhi].

Commentary: The preceding Ahadith described the practice of the Prophet (sallallaahu ’alayhi wa sallam) while the present one tells us about his order that one should lie down on his right side after offering the two Sunnah of Fajr prayer. Thus, this practice is proved by his speech as well as action which does not leave any doubt about it being a Sunnah and Mustahabb (desirable).