Al-Matalib al-'Aliyah 3790 — Surah al-Ikhlas

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) asked: "Is any one of you unable to recite a third of the Qur'an before he sleeps?" It was said: O Messenger of Allah (peace and blessings be upon him), who has the ability to recite a third of the Qur'an before sleeping? He (peace and blessings be upon him) said: "Whoever recites 'Say: He is Allah, the One' [Surah al-Ikhlas: 1], 'Say: I seek refuge in the Lord of the daybreak' [Surah al-Falaq: 1] and 'Say: I seek refuge in the Lord of mankind' [Surah al-Nas: 1], it is as if he has recited a third of the Qur'an."
Imam al-Tayalisi recorded it in his Musnad; the narrator Muhammad bin Abi Humayd in its chain is weak; however, the virtue of Surah al-Ikhlas and its being equal to a third of the Qur'an are established by other reliable and sahih hadith.