✅Answer: In narrations, the Witr prayer is referred to both as the three-rak'ah prayer that is performed after the 8 rak'ahs of the night prayer, and as the third rak'ah of it which is performed separately. The first two rak'ahs are called Shafa'.

The recommended surahs in these three rak'ahs are as follows:

1 ابن سنان قَالَ: سَأَلْت أَبَا عَبْداللَّه عن الْوَتْرِ مَا يُقْرَأُ فِيهِنَّ جَمِيعاً فَقَالَ بِقُلْ هُوَ اللَّهُ أَحَدٌ قُلْتُ فِي ثَلَاثَتِهِنَّ قَالَ نَعَم

📚Al-Kafi, Vol. 3, p. 449

Ibn Sinan said: I asked Imam Sadiq (peace be upon him) about the Witr prayer, what surahs are recited in all of its rak'ahs? He said: With 'Qul Huwa Allahu Ahad' (Surah Al-Ikhlas)! I said: In all three rak'ahs? He said: Yes.

2 عن أَبِي عبداللَّه قال كَانَ أَبِي يَقُولُ قُلْ هُوَ اللَّهُ أَحَدٌ تَعْدِلُ ثُلُثَ الْقُرْآنِ وَ كَانَ يُحِبُّ أَنْ يَجْمَعَهَا فِي الْوَتْرِ لِيَكُونَ الْقُرْآنَ كُلَّهُ

📚Tahdhib, Vol. 2, p. 127

Imam Sadiq (peace be upon him) said: My father used to say: 'Qul Huwa Allahu Ahad' is equal to one-third of the Quran, and he loved to combine it in the Witr prayer so that it would be (equal to) the entire Quran!

3 سُلَيْمَانَ بْنِ خَالِدٍ عَنْ أَبِي عَبْدِ اللَّه قَالَ: الْوَتْرُ ثَلَاثُ رَكَعَاتٍ تَفْصِلُ بَيْنَهُنَّ وَ تَقْرَأُ فِيهِنَّ جَمِيعاً بِقُلْ هُوَ اللَّهُ أَحَدٌ

📚Tahdhib, Vol. 2, p. 127

Imam Sadiq (peace be upon him) said: The Witr prayer is three rak'ahs which you separate (i.e., its two rak'ahs are separate and the other one rak'ah is also separate) and in all of them you recite 'Qul Huwa Allahu Ahad'!

4 مُعَاوِيَةَ بْنِ عَمَّارٍ قَالَ: قَالَ لِي اقْرَأْ فِي الْوَتْرِ فِي ثَلَاثَتِهِنَّ بِقُلْ هُوَ اللَّهُ أَحَدٌ.

📚Tahdhib, Vol. 2, p. 128

Mu'awiyah ibn Ammar said: (Imam Sadiq, peace be upon him) said to me: In each of the three rak'ahs of the Witr prayer (after Al-Fatiha) recite 'Qul Huwa Allahu Ahad'!

5 أَبِي عُبَيْدَةَ الْحَذَّاءِ عَنْ أَبِي جَعْفَر قَالَ: مَنْ أَوْتَرَ بِالْمُعَوِّذَتَيْنِ وَ قُلْ هُوَ اللَّهُ أَحَدٌ- قِيلَ لَهُ يَا عَبْدَ اللَّهِ أَبْشِرْ فَقَدْ قَبِلَ اللَّهُ وَتْرَكَ.

📚Amali al-Saduq, p. 58, hadith 8

Imam Baqir (peace be upon him) said: The one who recites his Witr prayer with Surah An-Nas, Al-Falaq, and 'Qul Huwa Allahu Ahad', it is said to him, 'O servant of Allah! Glad tidings to you, for Allah has accepted your Witr prayer!'

6 يَعْقُوبَ بْنِ يَقْطِينٍ قَالَ: سَأَلْتُ الْعَبْدَ الصَّالِح عَنِ الْقِرَاءَةِ فِي الْوَتْرِ وَ قُلْتُ إِنَّ بَعْضاً رَوَى قُلْ هُوَ اللَّهُ أَحَدٌ فِي الثَّلَاثِ وَ بَعْضاً رَوَى فِي الْأُولَيَيْنِ الْمُعَوِّذَتَيْنِ وَ فِي الثَّالِثَةِ قُلْ هُوَ اللَّهُ أَحَدٌ- فَقَالَ اعْمَلْ بِالْمُعَوِّذَتَيْنِ وَ قُلْ هُوَ اللَّهُ أَحَدٌ.

📚Tahdhib, Vol. 2, p. 127

Ya'qub ibn Yaqtin said: I asked the righteous servant (meaning Musa ibn Ja'far, peace be upon him) about the recitation in the Witr prayer and said: One person narrated that in each of the three rak'ahs 'Qul Huwa Allahu Ahad' is recited, and another narrated that in the first two rak'ahs Surah An-Nas and Al-Falaq are recited, and in the third rak'ah 'Qul Huwa Allahu Ahad' is recited; so the Imam said: Act upon An-Nas and Al-Falaq and 'Qul Huwa Allahu Ahad'!

7 عَنْ رَجَاءِ بْنِ أَبِي الضَّحَّاكِ فِي حَدِيثٍ قَالَ: كَانَ الرِّضَا....

ثُمَّ يَقُومُ فَيُصَلِّي رَكْعَتَيِ الشَّفْعِ يَقْرَأُ فِي كُلِّ رَكْعَةٍ مِنْهُمَا الْحَمْدَ مَرَّةً و قُلْ هُوَ اللَّهُ أَحَدٌ ثَلَاثَ مَرَّاتٍ وَ يَقْنُتُ فِي الثَّانِيَةِ قَبْلَ الرُّكُوعِ و بَعْدَ الْقِرَاءَةِ فَإِذَا سَلَّمَ قَامَ وَ صَلَّى رَكْعَةَ الْوَتْرِ يَتَوَجَّهُ فِيهَا وَ يَقْرَأُ فِيهَا الْحَمْدَ مَرَّةً وَ قُلْ هُوَ اللَّهُ أَحَدٌ ثَلَاثَ مَرَّاتٍ وَ قُلْ أَعُوذُ بِرَبِّ الْفَلَقِ مَرَّةً وَاحِدَةً وَ قُلْ أَعُوذُ بِرَبِّ النَّاس مَرَّةً وَاحِدَةً وَ يَقْنُتُ فِيهَا قَبْلَ الرُّكُوعِ وَ بَعْدَ الْقِرَاءَة

📚Uyun Akhbar al-Ridha (peace be upon him), Vol. 2, p. 181

Raja' ibn Abi al-Dahhak narrated about the conduct of Imam Reza (peace be upon him) during his journey to Tus regarding the Imam's Witr prayer that:

Then he would stand up and perform the two rak'ahs of Shafa' prayer and in each rak'ah he would recite Al-Fatiha once and 'Qul Huwa Allahu Ahad' three times, and in the second rak'ah before the bowing and after the recitation, he would perform the qunut, and when he gave the salutations, he would stand up and perform the one rak'ah of Witr prayer and in it he would recite the du'a al-tawajjuh and Surah Al-Fatiha once and 'Qul Huwa Allahu Ahad' three times and 'Qul A'udhu bi Rabbil Falaq' once and 'Qul A'udhu bi Rabbin Nas' once, and in it he would perform the qunut before the bowing and after the recitation.

Imam Reza's Witr prayer (peace be upon him)