The other is from Musa ibn Talhah, from his father. It was reported by Muslim, Ibn Majah (2470), and Ahmad (1/162).

Note: In al-Ziyadah ‘ala al-Jami‘ al-Saghir, al-Hafiz al-Suyuti distinguished between Muslim’s narration, attributing it to Anas, and Ibn Majah’s narration, attributing it to Anas and ‘A’ishah! This distinction is baseless, as you can see. *

3978—“Gather together, for I shall recite to you one-third of the Quran.” So those who gathered did so; then the Prophet of Allah—peace and blessings be upon him—came out and recited: “Say: He is Allah, the One.” Indeed, it is equivalent to one-third of the Quran.

It was reported by Muslim (2/200), al-Tirmidhi (2900)—who authenticated it—and Ahmad (2/429), through Abu Hazim, from Abu Hurayrah, who said: The Messenger of Allah—peace and blessings be upon him—said: … and he cited it up to the words, “I shall recite to you one-third of the Quran,” adding:

“So those who gathered did so. Then the Prophet of Allah—peace and blessings be upon him—came out and recited, ‘Say: He is Allah, the One,’ then went back inside. Some of us said to one another, ‘I think that news came to him from heaven, and that is what caused him to go inside.’ Then the Prophet of Allah—peace and blessings be upon him—came out and said: ‘I told you that I would recite to you one-third of the Quran. Indeed, it is equivalent to one-third of the Quran.’”

The wording is that of Muslim.

Al-Tahawi also reported it through this chain, in abridged form, in Mushkil al-Athar (2/80).

Ibn Majah also reported it through another chain from Abu Hurayrah: “Say: He is Allah, the One” is equivalent to one-third of the Quran. *