Al-Matalib al-'Aliyah 141 — 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.