Praise be to Allah.
The majority of scholars are of the view that it is better to offer the naafil prayers of both day and night two by two. Some scholars – such as Imam Ahmad – were of the view that it is obligatory to do it this way, and that these prayers are not valid if more than two rak’ahs are done with one tasleem, except for Witr, because of the reports to that effect in the saheeh Sunnah.
They quoted as evidence for that the hadeeth of Ibn ‘Umar (may Allaah be pleased with him), according to which the Prophet (peace and blessings of Allaah be upon him) said: “The prayers of the day and night are to be offered two by two.” Narrated by al-Tirmidhi, 597; Abu Dawood, 1295; al-Nasaa’i, 1666; Ibn Maajah, 1322. This hadeeth was classed as saheeh by Shaykh al-Albaani in Tamaam al-Mannah, p. 240.
What is meant by “two by two” is two rak’ahs by two rak’ahs. This is how it was explained by Ibn ‘Umar (may Allaah be pleased with him).
In Saheeh Muslim it is narrated that ‘Uqbah ibn Hurayth said: I said to Ibn ‘Umar: “What does two by two mean?” He said: “Saying the tasleem after each two rak’ahs.”
Shaykh Muhammad ibn Saalih al-‘Uthaymeen said:
The words two by two mean that you should not pray all four rak’ahs together, rather you should pray them two by two, because it is proven in Saheeh al-Bukhaari and Saheeh Muslim from Ibn ‘Umar that a man asked the Messenger of Allaah (peace and blessings of Allaah be upon him): “What do you think about the night prayers?” He said: “Two by two, then if any one of you fears that dawn will come, let him pray one rak’ah and that will make what he has prayed odd-numbered for him.”
With regard to the word al-nahaar (day), this was narrated by the authors of al-Sunan, and the scholars differed to whether it is saheeh or not.
The correct view is that it is proven, as it was deemed to be saheeh by al-Bukhaari.
Based on this, the nighttime prayers and the daytime prayers should both be offered two by two, saying the tasleem after each two rak’ahs. Every hadeeth which mentions four rak’ahs without clearly stating that the tasleem should not be said should be interpreted in this manner, i.e., it should be understood as meaning that the tasleem should be said after each two rak'ahs, because this is the principle, and minor issues are to be understood in the light of the basic principles.
‘Aa’ishah said that when she was asked about how the Prophet (peace and blessings of Allaah be upon him) prayed in Ramadaan, she said: “In Ramadaan and at other times he did not pray more than eleven rak’ahs. He would pray four, and do not ask how beautiful and how long they were.” This would appear to mean four rak’ahs with one salaam, but it should be interpreted according to the general principle, which is that the nighttime prayers are offered two by two, as that was proven from the Messenger of Allaah (peace and blessings of Allaah be upon him). It may also be said that she mentioned four on their own, then four on their own, because he would pray four and then rest, as is indicated by the word thumma (then) which is indicative of the sequence of events and also suggests a slight pause between the events described.
Al-Sharh al-Mumti’, 4/76, 77
In his Saheeh (2/214), Ibn Khuzaymah included the hadeeth of Ibn ‘Umar in a chapter which he called Baab al-Tasleem fi kulli Rak’atayn min Salaat al-Tatawwu’ Salaat al-Layli wa’l-Nahaari jamee’an (Saying the tasleem following each two rak'ahs of voluntary prayer during both the night and the day). He followed this with a chapter entitled Baab Dhikr al-Akhbaar al-Mansoosah wa’l-Daallah ‘ala Khilaaf Qawli man za’ama anna tatawwu’ al-Nahaar arba’an la mathna (Reports which indicate the opposite of the view of those who claim that the voluntary daytime prayers are to be offered four by four not two by two), in which he quoted a great deal of evidence to show that the voluntary daytime prayers are to be offered two by two.
The hadeeth, “May Allaah have mercy on those who pray four (rak’ahs) before ‘Asr” is to be understood in the manner explained above, which is that they are to be offered two by two.
Ibn Hibbaan said:
When the Prophet (peace and blessings of Allaah be upon him) said “Four”, he meant with two tasleems, because in the report of Ya’la ibn ‘Ata’ from ‘Ali ibn ‘Abd-Allaah al-Azdi from ‘Ibn ‘Umar, it says that the Prophet (peace and blessings of Allaah be upon him) said: “The prayers of the night and the day are (to be offered) two by two.”
Saheeh Ibn Hibbaan, 6/606. He also said something similar – in 6/631 – regarding the four rak’ahs which are to be offered after Jumu’ah prayer.
Shaykh Ibn Baaz (may Allaah have mercy on him) said:
What is prescribed is for the Muslim to offer the naafil prayers of the day and the night two by two, because the Prophet (peace and blessings of Allaah be upon him) said: “The night prayers are (to be offered) two by two” (saheeh – agreed upon). And according to a saheeh report he said: “The prayers of the night and the day are (to be offered) two by two.” Narrated by Imam Ahmad and the authors of al-Sunan with a saheeh isnaad.
Majmoo’ Fataawa al-Shaykh Ibn Baaz, 11/390
See also the answer to question no. 1048 for more details on the regular naafil prayers.
And Allaah knows best.