It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Companions (may Allah be pleased with them) would wait for the Isha prayer until their heads nodded from sleep; then they would pray and not perform ablution.
(b) Imam Abu Dawud (may Allah have mercy on him) says that Shu'bah, from Qatadah, added the words that this was the practice in the time of the Messenger of Allah (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 590
It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Companions (may Allah be pleased with them) would fall asleep (while sitting), then stand up and pray. These people did not perform ablution (on account of it) in the time of the Prophet (peace and blessings be upon him) (either).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 591
It is narrated from Sayyiduna Anas (may Allah be pleased with him): I saw the Companions (may Allah be pleased with them) being woken up for the prayer, and I would hear the sound of their snoring; then they would stand up and pray, and they did not perform ablution.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 592
It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Isha prayer was called to begin, and a man stood up and said: O Messenger of Allah, I have a need. He (peace and blessings be upon him) stood speaking privately with him until the people, or some of them, dozed off; then he (peace and blessings be upon him) led them in prayer and did not perform ablution.
(b) In Sahih Muslim the words 'and he did not mention ablution' are not present.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 593
It is narrated from Nafi' (may Allah have mercy on him) that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) would fall asleep while sitting, then pray without performing ablution.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 594
It is transmitted from Sayyiduna Ibn Abbas (may Allah be pleased with them both) in mawquf form: Whoever falls asleep while sitting, his ablution (remains); and if he lies down, ablution is due upon him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 595
It is narrated from Sayyiduna Hudhayfah bin al-Yaman (may Allah be pleased with him): I was sitting in the mosque of Madinah, my head nodding (from sleep), when a man embraced me from behind. I turned and saw that it was the Prophet (peace and blessings be upon him). I said: O Messenger of Allah, is ablution due upon me? He (peace and blessings be upon him) said: "No, not until you lay your side down."
Only Bahr bin Kunayz al-Saqqa narrated this hadith from Maymun al-Khayyat; he is da'if (weak), and his narration is not used as proof.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 596