Wudu after sleep

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: "When one of you sleeps lying on his side, he should perform ablution." It was said to him: But the Prophet (peace and blessings be upon him) used to sleep lying on his side and did not perform ablution again (for the prayer)? He replied: "You are not like the Messenger of Allah (peace and blessings be upon him); and if there had been any such matter (like ablution being broken by sleep) in the case of the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) would have known it best."
Imam Ibn Abi Shaybah narrated this report (athar) in his book 'al-Musannaf' (hadith: 593). In its chain, the memory of the narrator al-Mas'udi (Abd al-Rahman bin Abdullah) became confused (ikhtilat) in the last part of his life; however, this narration presents an important juristic inference of a Companion of the Messenger of Allah in the chapter on sleep invalidating ablution.

It is narrated from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) that he said: "When a man lays his side on the ground (in order to sleep), he should perform ablution."
In the chain of this report (athar), the narrator named Muhammad bin Umar al-Waqidi is matruk (abandoned) and severely da'if (weak), because of which this narration is extremely weak in its chain.

It is narrated from Harmalah, the freed slave of Sayyiduna Zayd bin Thabit (may Allah be pleased with him): I asked Sayyiduna Zayd bin Thabit (may Allah be pleased with him) for a legal ruling about sleeping while sitting, and he saw no harm in it (that is, he did not consider it to break ablution). I said: What is your view if I lay my side on the ground (to sleep)? He said: "Then perform ablution."
In the chain of this narration, Muhammad bin Umar al-Waqidi and Ibn Abi Sabrah are matruk (abandoned) and severely da'if (weak) narrators; moreover, Asim bin Ubaydullah has also been declared da'if (weak) due to poor memory. Therefore, by scholarly and technical standards, this narration is weak in its chain.

It is narrated from Sayyidah Aishah and Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) that they both said: "Whoever sleeps in any posture in such a way (deeply) that he is no longer aware of anything around him (that is, his reason and awareness are overcome), he is required to perform ablution again."
From this report (athar) the juristic principle is derived that sleep in itself does not invalidate ablution; rather, the loss of reason and awareness is the cause of ritual impurity (hadath). Therefore, if sleep is so deep that a person becomes unaware of his state, repeating the ablution becomes obligatory.

It is narrated from Imam al-A'raj (may Allah have mercy on him) that he said: "I saw Sayyiduna Abu Hurayrah (may Allah be pleased with him) fall (so deeply) asleep while sitting that I could hear the sound of his snoring; then he would get up and pray, and he would not perform ablution (again)."
Takhrij and grading: The chain of this report (athar) is sahih (authentic). This narration indicates that sleep while sitting firmly does not break ablution.

It is narrated from Hajjaj that he mentioned before (Imam) Ata bin Abi Rabah (may Allah have mercy on him) the state of the sleep of the Prophet (peace and blessings be upon him): that he (peace and blessings be upon him) would (at times) sleep so deeply that the heavy sound of his (peace and blessings be upon him) breathing could be heard, then he (peace and blessings be upon him) would (wake up and) pray (without a fresh ablution). At that Ata (may Allah have mercy on him) said: "The Prophet (peace and blessings be upon him) was not like other people (in the matter of ablution remaining intact during sleep)."
Imam Abu Ya'la narrated this narration in his Musnad. Although its narrator Hajjaj bin Artat is criticised with regard to his memory, its content fully agrees with the authentic hadith of Sahih al-Bukhari and Sahih Muslim which state explicitly that the pure heart of the Prophet (peace and blessings be upon him) remained awake; that is why his (peace and blessings be upon him) sleep did not invalidate ablution as the sleep of other people does.

It is narrated from Sayyiduna Anas (may Allah be pleased with him), or from a group of the Companions of the Messenger of Allah (peace and blessings be upon him), that they used to lie down on their sides (while waiting for the prayer). Sayyiduna Anas (may Allah be pleased with him) also relates: "We would come to the mosque of the Prophet (peace and blessings be upon him) to pray and then wait for the prayer; some of us would doze off or fall asleep, yet they would not perform a fresh ablution (for the prayer)."
Hushaym said: "This (report) is not to be acted upon."