This issue is among the jurisprudential topics and has also something to do with theological themes. The details are beyond the scope of this article. However, what we can mention briefly here is the following:
There are narrations in both Shi'ah and Sunni sources[1] making reference to this incident. Some of those narrations have reliable and authentic chains of transmission including the narration reported in Ya'qub Kulayni's Al-Kafi. The narrator narrates from Imam Sadiq (AS) that he heard the Imam say: "One day, the Messenger of Allah (S) remained asleep during Dawn Prayers and (in reality) God, the Exalted, caused him to remain asleep until sunrise. This was a mercy from Allah upon people so that if anyone remained asleep and could not wake up for Fajr prayers and others reproached him for failing to offer prayers telling him, "You are not God-fearing in your prayers", this incident with the Prophet (S) is an example that could referred to by a person who misses his Dawn Prayers. Hence, if someone tells someone else: "You remained asleep during morning prayer," he would say in response,  "The Prophet (S) also remained asleep during morning prayers." This incident that took place with the Prophet (S) was a mercy from Allah on the people (so that anyone who remains asleep could remind him of the example of the Messenger of Allah (S)).[2]
There are other narrations seemingly contradicting this narration. For example:
1. There are narrations which clearly indicate that the Prophet and Imams, peace and benedictions of Allah be upon them, are infallible. Imam Sadiq (AS) narrates from Imam Ali (AS) that he said: "Among the attributes of the Imam is that he is immune to all major and minor sins, making no mistakes in giving any fatwa nor any error in answering questions and he does not err, forget or commit any futile actions."[3]
2. There are narrations which state:  "...وتنام عینه و لاینام قلبه ) which means "his eye sleeps but his heart does not sleep…".[4]
3. There are rational arguments put forth by Muslim scholars to prove the infallibility of the Prophet (S). For example they say, "The Prophet (S) was sent to people to guide them to the right path; thus, his behavior should be such that people accept him completely. A minor mistake on his part will discredit him resulting in the goals of prophethood not to be materialized. That is why God does not appoint someone as intermediary between Himself and people who is prone to mistakes and error resulting in the divine mission not to be fulfilled and people to distance themselves from him. In fact, when Allah ordains absolute obedience of someone, then his entire actions and conducts must serve as examples to be followed by people. Obviously, a person who commits mistakes cannot be followed as an example.
4. Another argument is consensus of scholars about the infallibility of Holy Prophet, peace be upon him and his family. That is why when confronting these narrations, Muslim jurisprudents are divided into two groups:
A) Some scholars have not accepted the narrations about the Prophet (S) missing his morning prayers saying that the narrations are inauthentic or the narrators are likely to have mistaken or the narrators may have fabricated the report or may have dissimulated, not to mention the fact that they are opposed to decisive arguments such as those put forth by the author of Jawaher al-Kalam[5] and the author of al-Hadaeq[6] and Sheikh Ansari[7], may Allah bless them.  
Late Mirza Jawad Maleki Tabrizi[8] and late Ayatollah Sayyid Mohsen Hakim[9], may their souls rest in peace, rejecting these narrations say, 'It is inferred from the tradition in which the Prophet (S) addresses his companions "… you have remained asleep in the land of Satan…"[10] that Satan is unable to tempt the Prophet as evidenced by the Quran[11] and other decisive proofs. It cannot cause him to become forgetful nor can it affect his sleep. Therefore, the very clause in the narrations which implies that they remain asleep due to satanic inculcations is a proof of the invalidity of the narration.
B) On the contrary, some scholars have accepted these narrations saying they are in no way in contradiction with other arguments and infallibility of the Holy Prophet (S). For example, Sheikh Saduq, may his soul rest in peace, considers these narrations as decisive and authentic.[12] He differentiates between a satanic forgetful mistake (sahv) and mistakes other than that. Sheikh Mufid has a different idea as compared to that of Sheikh Saduq. He also differentiates between the forgetful mistake of the Prophet (S) and his remaining asleep.  He rejects the idea that the Prophet (S) committed a forgetful mistake. It is inferred from his saying that he concedes the Prophet's remaining asleep.[13]
First Martyr, better known as Shahid Awwal, also says after mentioning these narrations: "I do not know of anyone who might have put aside these narrations owing to an illusion that they are opposed to the narrations regarding infallibility of the Prophet (S).[14] Sheikh Bahai says: "The Companions have accepted these narrations and that shows they have differentiated between the Prophet's sleep and his forgetful mistake and they have given fatwa in accordance with it. Late Muhammad Baqir Majlisi has also accepted these narrations. [15]
Among the contemporary scholars, as far as we know, Ayatollah Bahjat does not consider these narrations to be opposed to infallibility of the Prophet (S).[16]
In conclusion, we should reiterate that in view of the above arguments, we must not speak of the Prophet's sleep in a decisive manner because the narrations in this regard are likely to be inconsistent and prone to objection. We must exercise precaution when speaking about the status of the Prophet, peace be upon him and his family.

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