Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Sayyiduna Abu Huraira (may Allah be pleased with him) that I came with the Messenger of Allah (peace and blessings be upon him), and I heard a man reciting «قُلْ هُوَ اللَّـهُ أَحَدٌ . اللَّـهُ الصَّمَدُ . لَمْ يَلِدْ وَلَمْ يُولَدْ . وَلَمْ يَكُن لَّهُ كُفُوًا أَحَدٌ» “Say: He is Allah, the One; Allah, the Self-Sufficient; He neither begets nor is born, and there is none like unto Him.” (Surah Al-Ikhlas). The Messenger of Allah (peace and blessings be upon him) said: “It has become obligatory.” I asked him: O Messenger of Allah! What has become obligatory? He (peace and blessings be upon him) said: “Paradise.” Sayyiduna Abu Huraira (may Allah be pleased with him) said: I intended to go and give glad tidings to that man, but then I feared that I might miss the midday meal with the Messenger of Allah (peace and blessings be upon him), so I preferred the meal. Then I went to that man, but he had already left. The hadith of Ubaydullah Al-Aghar with Zayd bin Rabah has already passed [ ح۱۸۶] and the second part of Al-Mukhlis is completed. And all praise is due to Allah. The number of people from whom (Imam) Malik has narrated in this is thirty, and (according to the numbering of Abu Al-Hasan Al-Qabisi) the total number of hadiths is two hundred and thirty-four.

It is narrated from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) that a man heard another man reciting « قُلْ هُوَ اللَّـهُ أَحَدٌ», and he was reciting it repeatedly. The man who heard this mentioned it to the Messenger of Allah (peace and blessings be upon him) in the morning, as if he considered this to be a small act. The Messenger of Allah (peace and blessings be upon him) said: "By Him in Whose hand is my soul! Indeed, this (Surah Ikhlas) is equal to one third of the Qur'an."