The Book of Vitues

Riyad as-Salihin, The Book of Virtues
Book 9, Hadith 1011
Narrated 'Abu Sa'id Al-Khudri (ra):
A man heard another reciting Surat Al-Ikhlas repeatedly. The next morning he came to the Messenger of Allah (pbuh) and informed him about it as if he considered it to be of little reward. On that the Messenger of Allah (pbuh) said, "By Him in Whose Hand my soul is, this Surah is equal to one-third of the Qur'an."[Al- Bukhari].

Riyad as-Salihin, The Book of Virtues
Book 9, Hadith 1012
Narrated 'Abu Hurairah (ra):
The Messenger of Allah (pbuh) said, "Surat Ikhlas is equivalent to one-third of the Qur'an."[Muslim].

Riyad as-Salihin, The Book of Virtues
Book 9, Hadith 1013
Narrated 'Anas (ra):
A man said: "O Messenger of Allah! I love Surat-Al-Ikhlas [Say: He is Allah, (the) One]." He (pbuh) said, "Your love for it will admit you to Jannah."[At-Tirmidhi].